Messerschmitt Me 262 and P-80 Thrust, Drag, and Horsepower
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- Опубліковано 28 вер 2024
- Can you calculate the horsepower of a jet engine? Yes you can, and it actually matters for certain aspects of aircraft performance.
We will be using the Me 262 and P-80 Shooting Star for these calculations, which will lead to some interesting comparison data.
Plus I'll work a little bit of Spitfire Mk 14, de Havilland Hornet, and F-14 in there too.
If you find any math errors, please let me know, and I'll add them to the comment section. I'm not perfect, and I made those charts pretty quickly.
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No one else on UA-cam is putting out this kind of content, with this level of quality. Keep up the great work Greg!
Thanks, and I understand and love your user name.
@@GregsAirplanesandAutomobiles Well, I'm glad neither of us will have to answer to the Coca-Cola company!
LOL
@ I dont think it does, because thrust comes with expelling gas, not pushing it, of course combustion will slow down as the inlets get less air but besides that, 10,000 ibs of thrust should be apples to apples at any alt
@@cerdon4076 But would the surrounding air density effect how the gas is expelled?
The ME 262 is just a beautiful aircraft.
It sure is!
It has a certain pride and elegance missing in the allied jets of the era. Maybe even more beautiful is the Arado 234 v19: ua-cam.com/video/B5665Vb8-6Q/v-deo.html
It looks like an ugly pipe gun.
@@coryfice1881 no it doesn't
@@vadimpm1290 yes it does.
The unique thing about the 262 design is that the more you sweep the wing back the more area ruled it is, the second generation 262 was going to have the same sweep as the Sabre. That in addition with the v tail which would have greatly reduced frontal area would have made the second generation 262's an aerodynamic masterpiece.
The reduction in frontal area from sweeping the wings would be relatively minor. The vast majority of the drag reduction would be from less wave drag due to less spanwise flow. That is the real benefit of wing sweep for transonic and supersonic flight.
@@dogeness the reduction in frontal area would have been the reduction in tail surfaces from 3 to 2. The unique benefits to increasing the wing sweep in the 262 would be because it would significantly increase the benefits of "area rule". This is an important aerodynamic concept discovered in 1944 Germany.
@@shawns0762 1. Didn’t kno that about the tail surfaces. Makes sense.
2. It’s both. It’s the area ruling AND the lessening of spanwise flow. This was the reason wing sweep was done on transonic jets. Area ruling is a separate concept and was discovered afterwards. If, as you say, it is true that sweeping the wings back on the 262 makes it obey the area rule, that is purely a coincidental effect and not the original intended purpose. Many swept wing jets didn’t follow area ruling. The Sabre and Mig-15/17 didn’t. Their wing sweep was purely to decrease spanwise flow at transonic speeds.
@@dogeness Yes, increasing the wing sweep would have made it faster regardless of the increased area ruling. It was about to get afterburning turbojets as well which would have increased power by about 25%.
I have been curious about p80 and me262 performance for years. Your research and presentation is top notch. Well done Sir!
I recently stumbled upon the Kommandogërat, a hydrolic-electro-mechanic control unit for the BMW 801 on the Fw190, very complex, very overengineered and very german. It looks like an interesting pre-electronic all-included computing device but can't find good info. This is the channel to ask for a video that goes deep on it. Anyway thanks for your content, Greg!
I'll cover it at some point.
Good stuff Greg, and I'll have a look at Aerodynamics for Naval Aviators. Thanks for the recommendation.
Thanks Central.
Don't remember this one, so I must have missed it when you first posted it. Once again, for a non-engineer audience, you managed to make most of the relevant information understandable, an accomplishment in itself (my math abilities are strictly upper-elementary school - arithmetic, fine, algebra and above, near-zero). Nicely done.
This channel is where the term "my brain is full" applies best. Thanks for an excellent video that makes me think.
I feel the same! I'm not a pilot or engineer or technician or anything. Just an enthusiast with a superficial knowledge of physics and engineering. But can anyone tell me if i am onto something with regards to my thoughts around induced and parasite drag?
Could it be said that induced drag is caused by effects such as flow separation and drag caused by shear or interactions with the boundary layer? (unsure of exact terminology in this area)
While parasite drag is the energy needed for the airplane to redirect the flow of air around itself (could this this be simplified as action=reaction between the panel being forced into the air and having to accelerate it out of the way? Inertia from the mass of the air molecules?
If i am onto something here it seems to make sense to me to be the reason why parasite drag is v^2. (But that may come just from my basic physics knowledge)
With induced drag, if i am thinking correctly here, it seems to make intuitive sense also that the airflow becomes more "sticky" and less likely to separate from the surface and create vortices and perhaps other effects.
Would love some better educated input if anyone is able and willing.
Thanks
Two thing about power:
1. Power (which animal lovers call horsepower) is rate of energy transfer.
There is a law about energy conservation, but there is no law about power conservation.
Shaft power is rate of transfer from fuel to crankstaft. Flight power is
rate of energy transfer from fuel to airplane. They are not the same or generally equal.
2. As speed increases energy transfer from fuel to plane (or fuel to crankshaft
or whatever) becomes more efficient. Why? Because we transfer energy by doing
work. While things are constant,
work = thrust X distance_over_which_we_apply_thrust
When a thing goes faster distance_over_which_we_apply_thrust increases, so work
increases and power increases.
I like your videos. They appeal to both the WW2 buff in me and the engineer in me. Good job!
As a former fighter pilot (F-16), I can say this is pretty awesome stuff. Only thing I would say is max G limit typically is not a factor based on the pilot, but on aircraft structural limits above which you'll start stressing the airframe at least to the point of shortening its useful life, and perhaps even to warp or break the structure. Typically, post-WW II USAF jets were stressed to 7.33 Gs (though not always) and as mentioned in the video, the Navy tended to use 7.5 (F-14 was designed that way but eventually limited in practice to 6.5 to save airframe life). The F-16 was the first jet that increased that to 9Gs over the entire flight envelope (the F-15 has a weird G limit that varies within the flight envelope, initially limiting it to 7.33 until the addition of an aural G Overload Warning System which allowed 9Gs in some portions of the envelope). We see this philosophy continuing with the F-35, with the A model rated to 9Gs and the C (Navy) version to 7.5Gs only (USMC B models are 7Gs, but that's because the lift fan increases weight and reduces structural strength quite a bit). Anyway, really excellent material, keep up the good work!
Great information, thank you. The structural limits of most WW2 fighters are well above 7Gs, hence I went with 7 as I felt it's a good number for a typical pilot.
@@GregsAirplanesandAutomobiles Yes, that's right, you did well for that specific case. I just did not want viewers to think that was kind of the universal principle. In any case, that was the first of your videos I have seen, but I am going to subscribe. That was really, really well done.
@@GregsAirplanesandAutomobiles Also, regarding pilot limitations, more accurate would be to have one limit for instantaneous G and one for sustained G. I know in your examples here the sustained Gs are not all that high, so not an issue (it was a factor in the F-16 for sure!). But perhaps 7Gs is a little low for instantaneous G. It really depends on use of G suit or not (in WW II some planes had those, but most did not), and of course each individual is different (short, muscular people tend to do better). Most trained fighter pilots can probably take at least 9Gs for a few seconds, sometimes more. But anyway, minor point with no real impact on your video. Just for future reference.
I talk about that a bit in another video. During WW2 the USAAF considered 4Gs as the maximum sustainable. Thank you for subscribing, I appreciate it.
@@GregsAirplanesandAutomobiles OK, I guess I need to catch up with your videos! I did not know about the 4Gs, it sounds a bit low, but then, I should not judge from the modern perspective with really nice G suits, and especially superior G-force training (the modern G-straining maneuver is critical to sustaining Gs). In any case it does not sound completely unreasonable.
From the perspective of pure physics (or mechanics, rather), the concept of "propulsive power" goes as follows:
The definition of mechanical work is W = F s (force applied over a certain distance).
The definition of power is P = W/t (work done in a certain time).
The definition of velocity is v = s/t (distance crossed in a certain time).
Substituting the above to the equation of power, you get
P = F s / t
...and since s/t equals velocity, the equation for power can be written as
P = F v
or, "power is the product of force and velocity". In aircraft context, the force is the thrust, and velocity is the true airspeed. In other words, the "power" is the rate at which the aircraft is doing work (moving through air) against the drag force (which at steady state flight is equal to thrust). By the way, the units in this formula should be SI-units: Newtons for force and metres per second for velocity, which will result in power in watts. Using other units requires corrective factors, as was shown in the video. All of the formulas in the video were correct, though in my opinion unnecessarily complicated because of US Navy... ;)
This concept of "propulsive power" is physically very real thing, but I find it a bit of an esoteric concept. At sea level where true airspeed is practically equal to calibrated airspeed, it makes some sense and can be a reasonably useful tool for calculations. Otherwise, its usefulness is limited and in almost all situations it's more sensible to just refer to the jet engine's performance with its thrust.
The thrust of a jet engine varies with airspeed, so using values from static thrust measurements doesn't necessarily give correct results at higher airspeeds. In fact, treating thrust as a constant value is almost bound to produce incorrect results, especially when you're trying to calculate sustainable top speed or maximum sustainable rate of turn (which is the same as calculating the top speed but with increased load factor). It can give you a ballpark figure for sure, but in practice you would have to look at how much actual thrust the engine is producing at a particular airspeed.
If the difference between static thrust and thrust at particular airspeed is significant, then it could obviously affect the estimated sustained G-force in turn as well.
A typical thrust/airspeed curve shows a high value at zero airspeed (static thrust), then it starts to decrease due to drag losses, then it starts to go back up due to ram air effect assisting in the compression of air. Some jet engines actually produce more than static thrust at very high airspeeds (though I don't think any of the WW2 era jets did that). The design of the intake and the engine itself obviously affects this a lot, and considering the P-80 and Me 262 used very different engines (centrifugal flow vs. axial flow compressors) and different intake ducting, I would expect a big difference in the thrust curves of these two aircraft. The P-80 would probably have more channel losses simply due to the length of the intake ducting and the amount of turns the airflow has to make, while the Me 262 would not be affected quite as much.
On the other hand, the P-80 had the engine concealed in a fairly streamlined fuselage, while on the Me 262 the engine nacelles were out there in the wind, so the difference in parasitic drag would also make a difference.
The formulas I used are straight out of the book I referenced. You may view them as unnecessarily complicated, but I'm not sure what I can do about that. The formulas you put up are nice, and certainly correct, but I think you understand why I have to go with the official stuff in my videos, at least official in terms of pilot training. Regarding thrust varying with speed. yes, it does do that. I mentioned it, and I put up the chart from the book showing it. Since it's a small variation that we have no way to quantify in these planes, I felt it made sense to leave it out of the calculations. Frankly I'm much more worried about the possible error with the 262's clean stall speed, that's the biggest possible variable here. Thanks for your post, it's quite good.
Thanks for your description of jet power. I find it's a difficult concept to grasp, but it helps to think of it as the rate of work done to oppose drag.
By the way, did you mean 'then it starts to go back *up*' in your second to last para?
@@ltflipper2 Yes, thanks for the correction.
@@GregsAirplanesandAutomobiles I understand the reason why you put the formulas in as they are in the source material, and why the source material has them in that form - because they want to keep using one unit for one thing (pounds for thrust and knots for airspeed in this case). Mixing and matching units is known to cause confusion, resulting in a wide range of accidents - from airliners running out of fuel (like the Gimli Glider) to Mars probes crashing due to software not doing unit conversion correctly.
I didn't mean that comment as a critique of the video, but just to point out that the physics equations themselves are simpler than the equations used in the aviation textbooks and such. That is the advantage of using SI units - the equations can be more representative of the underlying physics, while the more archaic units (like knots and pounds and horsepowers and such) always require some seemingly random numbers inserted into the equation to make it spit out the numbers in the desired archaic units.
Regarding the thrust variance of jet engines, I understand that sometimes there's just not enough information to work with and in those cases, using what you got is fine and usually gives results that are at least somewhat comparable to each other. The thrust variance was recognized as a possible error source, which is good.
There are theoretical ways of estimating the thrust variance as a function of airspeed but without some computational fluid dynamics simulation, you'd have to do some guesswork on how the airspeed affects the flow rate through the engine - and sometimes, it's just best to minimize guesswork altogether and use the available numbers even if you know the results aren't going to be 100% accurate. In most cases the results are at least going to be comparable to each other between different aircraft.
Luckily there is some information about this old tech - fragmented as it is, there is this image that looks like it comes from an original German document: i.imgur.com/qtQBoKo.jpg
Unfortunately I don't know exactly what document that image comes from, so I can't tell the exact context - except that it supposedly shows the thrust curves of a Jumo 004B engine at different altitudes and airspeeds. From the document, we can see that at sea level (H=0), the static thrust is almost 900 kgf but drops quickly as airspeed increases, going as low as 680-690 kgf at airspeed of 400 km/h, and then picking up towards higher airspeeds.
Since the difference can be as high as 25% of the full static thrust, I think it's fair to say it should be factored into the results, especially as the biggest thrust reduction effect happens just around the airspeeds mentioned in this video - 400 km/h is roughly 250 mph or 216 knots.
@@HerraTohtori The pic is in Russian (from their own after the war testing, may be?) and gives not only the curves of the engine thrust for different heights and speeds in SI units in the lower part, but also in the upper part the curves are the fuel consumption in kilograms per hour for a kilogram of thrust for the same heights and speeds, presumably for a single engine.
You do a phenomenally good job of teaching flight principles and improving the understanding of competitive fighting envelopes in combat aircraft.
Thank you. I am trying here.
Wow, great video...so much great information. Enjoyed it a lot. Always happy to see a new video from you. Wow!
Thanks Carl. I'm glad I made this one, as it takes care of a lot of principles I'll need to reference in the future.
Your channels is my favorite, I’m a Pilot, and a A&P and can’t tell you how much I enjoy watching your well done videos. Also agree with your ranking of the P-47. The Spitfire and Mustang are indeed elegant, but the P-47 hits my buttons in most categories. Obviously range is the Mustangs domaine. I appreciate what you do, and know your videos will be watched as long as this society survives. Best Regards
I have found that Gregg knows more about the Airplane than most people ever. I don't know how you know so much but your videos are very informative and interesting. Thank you.
Your dissertation on the L/D, induced drag, parasite drag and total drag reminds me of primary flight training. A good visual example of 'getting behind the power curve' can be seen in videos of the 'Sabre Dance"{F-100} and the F-16 crashes when dropping below the minimum speed on landing approach. Even an above-1-1 power to weight ratio can not assure recovery from this attitude. Love your videos, and the fine details brought forth. A refreshing break from mainstream, myth-ridden history of all these fine aircraft.
Hi Greg! I would love to see you do a video comparing characteristics of early Jet fighters with late "Superprop" fighters. For example, why do early jets have such horrible acceleration at low speeds?
Most early jets were slow to spool up, and in the case of the 262, it has a lot of induced drag at low speeds.
Very interesting, as a mere life sciences grad, the non intuitive maths is very enlightening and obvious when you think about it which of course I didn’t initially 🙈 Thanks for a mathematical workout - I always learn lots from your videos Greg!
Finally... Some one is doing real comparison of WWII Jets! Great job mate!
Impressive reconstructive effort. There isn’t a whole lot of data on these planes, and it’s really awesome to see the effort that you put into this.
Thank you.
Greg's Airplanes and Automobiles You are most welcome. I want to compliment your methodology in choosing data when there are no hard numbers. The fact that you came to the same Optimal Climb Speed for the ME-262 as the manual shows how good at that you are.
26:40
If you using excel or pretty much any other spreeadsheet software, you can change a setting in the graph making them interpolate any value between giving a really good estimation if intermediate values.
I had heard the 263 was originally to have a straight plan form wing. However the Jumo engines were front heavy, so they returned the centre of balance by sweeping the wing, thus moving its CG to an ideal, just to the pilots rear as intended.
GREG IS BACK!
Praise the lord of airplanes and automobiles!
That put the P51 versus ME262 Hollywood dogfights into perspective. There is just no possible way that a piston engine fighter can sustain a dogfight at reasonable speed with a Jet. On the lower speed range it appears that the Sopwith Camel can easily out-turn the P80 and ME 262. The future belongs to the Sopwith Camel!
Another great book is Introduction to Flight by John Anderson. We use it in my university aerodynamics class. It’s very understandable and breaks down these similar concepts. However it costs money. Great video as usual!
Great art at 11:26. I enjoy your outstanding explanations of aircraft and auto performance.
The art is straight out of the 1945 P-80 pilot's manual. I like to use that because it's free, historically relevant, and I just like it.
It’s good stuff!
Top notch. Clear and relevant to jet aircraft performance. Kudos!
To clear up the correct spelling of the ME262‘s name...
I‘m german and very old 😂. In all older german documentaries, wochenschauen or pilot interviews it was always the „MEH zweizweiundsechzig“, means „MEH twosixtytwo“. Not „M.E. Two six two“.
I also noticed that in modern english or even german documentaries the BF109 is mostly called „B.F. One O Nine“ while german pilots called it the „B.F. Hundred Nine“ or some the „MEH Hundred Nine“ or simply the „Hundred Nine“.
I‘m not saying this is the official correct spelling but i noticed this has changed since the rise of the internet.
I think it was called the me 109 by the allies in english more often but language works in funny ways ig
Reminds me of my hungarian grandmother, she used to say years as for example: nineteen hundred sixteen. When speaking english
Mr Greg,
It's possible to fill in all of the blanks for the 262 numbers. The Me-262 that Paul Allen's FHCAM museum restored to flying condition was done to all original specs, including the engines (but now with reliable metals).
Not sure where the specimen is at this time, with Mr Allen passing, and WalMart Walton kinfolk buying.
The excellent summer monthly fly days of the WW2 collection have not resumed. (And supposedly they will continue the Stuka build).
Last news, years dated, 262 was flight certified,
( by Hinton?).
You could probably obtain modern test numbers for the 262 that would be identical to 1945.
Cheers
Presentation is excellent, clear, not overloading the viewers ("students") w facts all at once but building up lvl of complexity at just the right rate as well as non-biased - just factual & objective. Continue...
Also, waiting for Parts #3/4 of the FW190 lectures..whenever the Muse strikes
***** 5 Stars: would watch again
Thanks, I appreciate it. After I finish the P-47 series, which has one more episode then I'll be in a good position to continue the 190 series.
Amazing video, the way you explained all these aerodynamics is incredible. Amazing video, hard to find such quality on UA-cam
I learned something today, thanks Greg!
Thanks Paddy. I really like your Spitfire and 190 chase video. That's some great footage you put up.
Perhaps you would consider doing a video on the British Electric Lightning F6. I'm a big fan of that one!
Pretty darned interesting. The concept of a piston engine not rotating a crankshaft at 20:34 might be able to use the average piston speed as your linear motion rather than the rotation of the crankshaft. What happens when you apply the same logic to a piston engine/propeller driven aircraft and determine it's relative propulsive horsepower, since you show a beautiful Packard built Merlin in your video, use a P-51 and a Spitfire in their top of the line designs for a similar comparison as the 262 vs the P-80? I see there's one for the P-51 vs the (which version, BF or ME?) 109 so half the comparison is already done. It would be very interesting to see how the numbers compare given two airplanes that are so dissimilar and yet used the same engine. Just for giggles and fun how about a later model P-47.
Discussing the F-14 reminds me of the demonstration they used to do at the Point Mugu Naval Air Station "Space Fair". The F-14 would do a 360 degree turn while keeping between the runway and the perimeter of the base. It was both scary and very very impressive both of the plane's capability and the pilot's ability to fly in such a edge of the envelope maneuver. He would be in a near 90 degree bank and full afterburner and you could see the pilot changing the bank angle constantly to avoid going over the edge. He did this only 150 or so feet above ground level, if that. I doubt he would have survived had the airplane stalled. Personally I think the navy gave up a huge advantage in air superiority when they retired the F-14.
Yep. Very interesting video. Otherwise I wouldn't have such a large comment. And near the end you did mention propeller driven aicraft but not a comparison of the 2 different planes with the same engine that I suggested. I won't kid myself that I could do it myself because I can't. I also won't kill myself is you never do it. But I do intend to watch your other videos.
Thanks
Chris
Hi Chris, I saw the Blue Angels perform in F4 Phantoms at Point Magu when I was very young. I just flew into Point Magu myself a couple weeks ago and talked to some Navy pilots. It really brought back memories.
As always, your video answers a great number of "why" questions. Super!
Thanks so much for making these. I learn a lot from it and feel I can trust it because you show your workings and sources. Great job.
Thanks for watching. I do try and not only list sources, but put the actual pages up (they are not copyrighted) so you can pause if needed and read it for yourself.
in some ways the p80 was more advanced than the me262 such as incorporating the jet engine into the fuselage. if you watch the history channel from years back, they would have you believe the nazis had laser guided bombs...
Well, they did have the first (extremely primitive) guided bombs
Greg: Its Henri again and I wanted to add a bit when you were discussing torque and the work done. Your channel is amazing and I am honoured to simply discuss this with you. Henri.
Hello Greg,
In your video on the P-80/Me262 there some aspects that I would like to point out as a physics teacher.
1. When anything has all the forces and torques balanced it is said to be in ‘equilibrium’. Now if the object is at rest this is naturally ‘static equilibrium’. If it is moving at constant velocity then the equilibrium is ‘dynamic’. This is even used in stars that maintain a given shape like our sun. Here it is a balance between the pressure caused by the fusion reactions and the rate at which the energy is transported versus of course gravity. Our sun does not materially change diameter due this balance and a star as stable as our sun would respond within 30 minutes to some force deflecting its radius by 10%, but I digress.
2. Regarding torque. Torque is analogous to force in the rotational variable world. So, we measure it in foot-pounds NOT pounds (for everyone but the US, it is Newtons and metres, but I digress). So, as I am sure that you know it is easier to open the door if you push on the side opposite the hinges. For a given door it takes a given amount of torque to cause it to rotate on its hinges. Torque is the vector cross product of the applied force and the moment arm position vector where the force is applied. Now, in much of the applications in aviation the force and the moment arm with encounter each other at right angles making the torque computation simply r x F (note though that there IS an angle here and F x r = - r x F). So to your point the nut is easier to loosen if you press on the wrench near the end orthogonal to the longitudinal axis of the wrench. Just to add in that it does look that displacement(sort of) x Force = Work and so the unit should be a Joule, BUT these are rotational variables and so all the mass does not move the same distance, it does move the same angle. So to distinguish this the units are left as compound units.
3. Energy, Work and Power. I find that the definitions of these are messed up a good deal in many books and forums. Energy is NOT the ability to do work. Why? Because work is defined as the amount of energy exchanged in a process so what people are saying is that work is work. How philosophical, but not much use as a technical definition. Furthermore, work occurs in all kinds of situations removed from mechanical ones (like burning gas in your car) and so to limit it to Force x displacement is inadequate. I have arrived at the definition of energy as the ability of an object to alter its circumstances. The rate at which it does so is the power. Now, given the definition of the energy/work in any situation you can take the time derivative and get an expression for the power. In linear cases it is Force x Displacement (not distance) and if the path is serpentine and so one then resorts to a line integral. However, when we consider the situation in rotational cases, the displacement is angular typically measured in radians (length of the unit circle that is subtended). If we consider the wrench loosening a nut, then the torque applied x the angular displacement should equal the work. Let is us see if this is so. Consider first the arc length that the hand pressing on the wrench travels. This would be then Force x arc length. The arc length is simply the moment arm x the angle in radians. So F x r x theta = torque x theta. And you get the work in a rotational situation. Effecting the time derivative would give the following. Assuming the force and moment arm is constant then you get Power = torque x angular speed. Now, in linear motion, we have the same arrangement. If we have Work = F x displacement (s) then a time derivation will give Power = Force x velocity (force being constant)
4. Work without motion. When I teach this, I say that there are TWO questions the both must be answered to be able to effect such a computation. 1. Which force is doing the work and 2. On which object. When you strain on a wrench and do not achieve any motion on the nut you are correct that no mechanical work is being done on the nut by the force/torque applied by the wrench. However, you ARE doing chemical work on yourself. When you flex your muscles, they do not care if the thing moves or does not move. Hence the success of isometric body building. You body in the act of flexing the muscle causes the circumstances to change. The process is about 60% efficient so the rest is heat which ultimately causes you to sweat. Even if you have a car standing on the brakes while it is revving up, there a helluva lot of work being done in certain aspects of the car, just not in moving the car proper
5. The hp of a jet engine. To my thinking, the jet engine, like the prop is doing work on the air. Yes, at different altitudes and such like things can be more or less efficient, BUT, from the engine’s standpoint, you are getting a certain amount of thrust. So, let us take the mass of air that is accelerated per second and assess what force it would take to do that (F = ma) and multiply that by the final air speed and you have the power on the ground. Aside from nuances of engine performance at various airspeeds and altitudes, the power seems to be disconnected from the performance of the airplane.
Hi Henri, that's quite a post. You clearly know more about physics that I do, or most other people. I appreciate your efforts here, and I'm certain everything you said is 100 percent correct. cont:
The statement that a jet produces zero horsepower when stationary creates some controversy and discussion. However I want to point out a few things. First, I'm not saying the jet isn't doing work, or generating power. It is, but it's thrust not horsepower. AFNA is the highest source I have on this and it makes it clear that with zero airspeed we can have a lot of thrust but zero horsepower. I think the same is true with the wrench analogy I used. If I have that wrench on a crankshaft, I can put all the torque I want into it, energy is certainly being used, but the horsepower measured at that crankshaft will be zero.
I love your post and I think it's the most complete explanation I have heard on this topic. Your students are lucky to have you.
There is a 5th component in addition to lift, thrust, weight and drag in order for an aircraft to fly...money.
Great work as always, Greg! I have been learning so much!
I geeked out so much with this video my head exploded a bit
Interesting comparison
My flight instructor told me one pound of thrust equals one horsepower at 375 Mph. I find that useful to do a quick calculation of power because I have difficulty conceptualising "thrust" compared to HP.
That's correct, or close enough, 325 knots is 374mph.
Think about it this way: A piston engine, propeller driven plane uses the propeller to convert the engine's horsepower into thrust from the burning fuel. However, the turbojet engine uses the burning fuel directly to produce thrust. Either way, it's the thrust produced by the engine that is acting against drag, not the engine's "horsepower".
*Greetings...Plane Whisperer....you have 100% of our attention*
I flew Avon Sabre and Mirage. Sabre glide 190 kts, climb 350 kts. Mirage glide 300 kts, climb 450 kts IAS
Just thinking. The turbine section drives a shaft that, in turn, drives the compressor section. There is some measurable hp there. The accelerated exhaust being the source of propulsion that is hard to calculate into hp.
Yes, we are talking about propulsive horsepower here.
Retired pilot here... Keep up the good work. And I salute you.
Thanks Mike, I hope you enjoy retirement.
@@GregsAirplanesandAutomobiles
LMAO... Well, to be honest, it sucks. Just saying.
You could always go fly for Ameriflight.
@@GregsAirplanesandAutomobiles
Well, yes. I could... But the entire bummer of ad hoc 135 is what convinced me to retire in the first place. So I'm thinking that maybe a better plan is to rent some hanger space somewhere and start building BD-5's or whatever.
Have you read the account of the P-47 pilot who got to do a test flight of a 262 right soon after VE day?
Thank you Greg, you make perfect sense
Awesome video as always, thanks a lot! Im a car mechanics and have absolutly no clue about aerodynamics and all the involved forces so i really enjoy watching these and learning some new things! Have a good week mate!
Thanks, Greg, for the good explanation of why power is proportional to speed with jet (and rocket as well) engines. I have lost count of the number of times I have been called stupid over this point. NASA uses the principal on deep space missions to get the most out of the available fuel load. Deep space probes will burn as they whip through perigee in the gravity well of the "slingshot" planets at high speed, thus gaining far more energy than if they were to burn at lower speeds before or after the encounter.
This is also the reason the takeoff acceleration feels so weird in an airliner. We are used to limited power cars that accelerate quickly from a stop, but run out of steam as speed builds and soon lack the power to sustain the acceleration rate. The jet takes a bit to spool up, but then the acceleration is sustained until the pilot rotates the nose for climb out....we are not used such a long period of sustained forward acceleration.
Next time someone calls you stupid, point them to this: en.wikipedia.org/wiki/Oberth_effect
@Brent Smith, awesome link. Thanks. I don't worry about people calling me or anyone else stupid, 9 times out of ten, the people who resort to name calling are the very ones who don't understand the subject matter.
I had aerodynamics for naval aviators at cal poly, unfortunately it's lost. It would be nice to have it and my notes, but such is life.
For the 262, are there numbers for lift, drag, Vx and Vy from the modern replicas that are flying? You could then adjust for the engine difference between original and replica.
I don't think so, but maybe.
I love these videos so much!! It is this kind of stuff that keeps me going :)
Most low altitude max climb rates in a jet are accomplished at a constant indicated or calibrated airspeeds. This requires a small amount of acceleration to maintain, while small, is not zero and is noticeable.
excellent, the aerodynamic advantages of the ME262 versus all Allied planes is very apparent. The 1945 Meteor performance would be lower than the P80. The parasitic drag of the Meteor would is higher than that of the ME262. I am very glad that I had the right (Russian) books about aerodynamics - i.e. your lecture about induced vers. parasitic drag. For the MIG21 the area where the engine power cannot overcome induced thrust is called "Regime II" (best to be avoided).
Hello Greg, sorry for the late comment but I have a question : at 44:00 you are calculating the amount of G's an Me-262 can sustain, yet when I do the calculation : square root of (3940 which is the engine thrust - 1251 which is the parasitic drag):300 I get 3.03 , while in your video you say 2.88, you presumably accidenctally even mention it having 3600 pounds of thrust but even then it doesn't work, am I missing anything?
Here's the man!
Top stuff....
Greg I may be delusional.. But as i see the 262 . It appears to have lift body fuselage incorporated into its design to what looks like an extremely well thought out use of balance. As far as lift/drag coefficient while maintaining function.. compared to other designs in early jets that simply seem to be chasing low drag numbers like the p-80 as a comparison??!
It does look a bit that way, but I don't have any data to support that either way.
One important factor about Me 262... that have pretty much nothing to do with what you say here, but is really important. Why Germans build Jet fighters. Its worth saying that British had a working Jet engine already in 1938.
At least according to most fact sheets i can find, the Jumo 004 engine was quite a bit worse than the Rolls-Royce Derwent or the Allison J33... Of cause.. that is in static test, i would imagine that Jumo 004 would gain quite a bit more from ram air recovery. being a axial engine.
Make sense designing the Me 262 with good high speed performance when the engine have it. Still the low speed performance was really very very lacking as was the low speed throttle response making the 262 so vulnerable during low speed it pretty much needed escort.
Now, the really important part is why the Germans thought it was worth it when British and US ... i would say, was thinking it was not worth it during the time. And the answer to this is seams to be really quite simple. Fuel quality.
Germans had simply not the capacity to produce higher quality fuel, and even the one they did they had very low capacity for. There was no margin of raising the volume of high octane petrol. US and UK as far as i know, never had that problem.
Jet, that run of fuel that is pretty much diesel, didn´t have that issue. This solve the problem, and is also the answer to why Germany designed all manner of attack and bomber aircraft with Jet where the advantage is limited to none.
2:00 I'd base my arguments NOT on any book but upon physics, fluid dynamics and general understanding of the principles involved.
That's great, but I can tell you that when you are in front of a designated examiner you won't get far with that. In fact, I learned this first hand on my CFI check ride with an FAA inspector back in the 1980's. (I passed). If I said something that I couldn't back up via an official document he would say something like "technically that may be correct, but officially it doesn't mean a damn thing". It's also important to remember than AFNA is probably the most peer reviewed book in existence on this subject, so I'm sure the fluid dynamics and physics in it are correct. Stick with it and you are on solid ground.
How TOTALLY fascinating, you are so logical and analytical, however I apologize the sound of your soothing logic voice has soothed me to sleep..lol...
4 years of college doing aerospace engineering, and they never once explained induced drag in such a simple and easy to understand way as you did. Idk if all colleges are scams, but mine sure as shit was
Sadly you may be right about colleges.
Thanks for a good video. If it's not too trivial to mention, your graph at 7:18 labels the minimum drag point as "Minimum drag or (L/D) max". The maximum L/D ratio is achieved where a straight line from the origin is tangential to the total drag curve, i.e. at a significantly higher speed than the minimum drag speed. It looks to me as though it is about 210 knots.
Just to clarify, that's not my diagram, it's straight out of Aerodynamics For Naval Aviators.
YEAAAHHH KEEP UP GREG THANK YOU MASTER.
Thanks !!!
There are a few pilots, student and otherwise, I am going to recommend this video too.
Oh, thanks :)
Waiting for Greg’s in depth discussion of a bumble bee vs a common dragon fly ……
Thanks, that was illuminating.
Fascinating stuff! Question: Does the power increase as the speed increases because you're pre-compressing more air at higher velocities - kinda like a naturally aspirated form of supercharging?
Hope that doesn't sound dumb... maybe i missed something. Thanks, Greg! Love your work!
Hi James, no, but I really can't explain it very well via text within the character limit here. I tried in the video, but it's a hard concept to get your head around.
So how does the first metor compare to the 262 at best ?
Poorly, the WW2 version of the plane had a long way to go. Now eventually the Meteor became pretty awesome, so if we compare a late 1946 Meteor to a WW2 262, then the Meteor is superior.
Back to the slide rule.
Glide distance doesn't vary with weight? If that is true, why did the crew always throw the kitchen sink out of the damaged bombers when trying to glide back home?
Glide distance does not vary with weight. However, engine out performance does, so lowering weight will help if trying to get home on one engine.
Thank you
I know at least 1 working replica has been built of the ME-262 have been built . Is it possible that could provide some data that would comport with what you have figured out with the historical data you have ?
I wonder how the me262 family would have evolved after seeing al those prototypes. Maybe actually turn into a sabre.
I really enjoy your content. Could you explain why the engine used on the 262 was shaped so as to make the opening smaller than the circumference of the engine? Does that shape force more air in?
Note that the minimum drag isn't exactly at the point where induced and parasitic drag are equal. What you can say is that the minimum drag is at the point that the slope of the curve of induced drag is equal to the negative slope of the parasitic drag curve i.e. dF/dv = 0. The fact that they look to be at the same point on the diagram shown is a bit of a coincidence and may be slightly misleading.
Aerodynamics for Naval Aviators says "Because of the particular manner in which parasite and induced drags vary with speed (parasite drag directly as the speed squared; induced drag inversely as the speed squared) the minimum total drag occurs when the induced and parasite drags are equal."
@@GregsAirplanesandAutomobiles Hmm okay if you assume scaling laws 1/v^2 for induced drag and v^2 for parasitic drag this checks out
Hi Bill, you may very well be right about that, but it's outside my scope of knowledge. Just keep in mind that I'm not assuming anything in regards to this specific topic. I am simply referencing the highest possible source on this topic, which is AFNA.
I learned a lot here thank you.
Based on these findings I think I'd rather fly the p-80. the 262 is faster and can turn at the p-80s top speed but for each maneuver each loss of speed the p-80s characteristics become more forgiving and the advantages of the 262 dissapear in a 20 mph window and at the very reaches of top speed. at least for now till the good man Greg releases more data to disprove this theory I'm glad my middle school thoughts that the p-80 was better is both simultaneously proved and disproved in one video. Cheers Shannon
I wouldn't argue that, a great argument can be made for the P-80.
Me-262 was supposed to attack bomber formations, not dogfighting fighters. But Me-262 pilots seems to favorize ambush attacks on fighters, because it's more safe than attacking a bomber in formation. The philosophy ot Me-262 was speed and firepower, not horizontal maneuvrability. And this is a right philosophy. Main problem for the germans was the lack of rare metals and natural oil. Not to win the war, just to make better planes.
@@VG-ey4gi if you would like to go down the supposed to rabbit hole it was supposed to be a bomber and not a fighter or bomber interceptor at all. In this scenario proposed by Greg I merely stated that in a fight between the two i would choose the more maneuverable aircraft and give up a bit of top speed. Speed only is not a 'right' philosophy because it has obviously failed and is not the direction of any modern war bird that isn't designed specifically for reconnaissance.
@@shannonnezul4903 No, it was designed as fighter, later they tried to adapt it to carry bombs.
@@shannonnezul4903 Not what the US and the USSR thought about it, producing first the fastest possible planes, only much later aiming at manoeuvrability
Vry bluntly stated wat does it means to be operational in ww2 i.e lukout
0:00 Kinda disturbing how they airbrushed Buck Dharma and the guys out of that photo.
44:00 Does this eventually lead to John Boyd's E-M theory?
"We are way above the amount of thrust our engine can offset .... we can pull the 5.4G but the plane will slow down very quickly."
I cover Boyd's work in another video, but it's one that gets very few views.
warthunder should watch this
How does water injection hsve any effect on a jet ?
It reduces temperatures.
Hi Greg, Excellent video. I have a question for you. Why didn't you compare the ME-262 to the British Meteor fighter?
I just didn't get to it. Including the Meteor would have made the video too long.
@@GregsAirplanesandAutomobiles Thanks Greg, your videos are very educational. It would have been an interesting match up if the Meteor and Me-262 did square off with equally capable pilots and a neutral start.
Wow, how did you tell the induced drag of a plane at a glance?
Please do a video on fighter wing designs and how the specific characteristics (ie. induced drag) reflect fighter design philosophy and performance.
Edit: at subsonic speed of course :D
The aspect ratio is a big key, Take a look at a U2 spyplane, long skinny wings and low induced drag.
Greg's Airplanes and Automobiles I think the wing twisting is a key too, Ta152H?
Also long skinny wing and short stubby wing of the same area, which one generates more parasite drag?
The TA152 is an interesting airplane because it's really the only prop driven fighter the Germans built specifically for high altitude. That's why it has that wing. As a general rule, short wings have less parasite drag, long wings have less induced drag. I'm simplifying here, because I can't do this justice in the comment section, but think of the Spitfire. The clipped wing version has less parasite drag and is faster down low, the non clipped wing has less induced, and is faster up at high altitudes.
The 262 redefined badass and is debatably still the legend of design. I like the Connie but that's different. I honestly cannot imagine a better looking jet. Some of the MiGs came close...here we come, flying to meet their thunder at 'em boys...I might have got that a bit wrong. I refuse to google the Air Force's theme song. I'll simpply rewrite it, like putting swept wings on an American airplane in 1944 cuz just because we're a bunch of egomaniacs doesn't mean that we cant' do what the Russians do and straight up copy the thing. America the Too Proud to copy swept wings. Where was Jack Northrop?
Ok, so I have little bit of a complicated question. From about 4:40 - 8:00 you talk about induced drag.
Now I understand what induced drag is, induced drag is the horizontal component of the lift force perpendicular to the cord.
Now, in the picture you show the airfoil with 0 angle of attack (AoA) would also have zero induced drag because it isn't generating any lift force.
Now for the part I don't understand, in the total drag chart which shows both induced and parasite drag, what is producing the induced drag in the steady state flight?
Induced drag has to come from having some kind of AoA, but if I'm flying level, there wouldn't be any induced drag?
Maybe you can help me out with one more thing. I'm trying to construct a drag chart for the Fw 190A-5, and as you have stated it is very difficult to find information. All I have come up with are three leads, a stall speed of 118mph, possible best climb of 175mph, and a max range speed of 270pmh (this one feels way too high from plugging it in). I played around with the numbers a bit, and I'm not sure which one is right. Do you have any data from your own research?
In steady state level flight almost all aircraft are flying with some amount of positive angle of attack. The lower the speed the higher the angle of attack and thus the greater the induced drag. Now there is an exception, certain wing designs can produce lift with no angle of attack, but even these can't produce enough lift to hold up the plane at the speeds at which they fly without some angle of attack. So in practical terms you could say that all airplanes in steady state level flight have a positive angle of attack.
Making charts for German planes is a problem for the reasons you stated. In fact, I think I need to remake my 109F chart, because the best glide speed I used, which was right out of a 109 manual may not be the literal best glide speed. I don't think I have seen a best glide speed for the A5, but 270KPH which would be 168mph does sound reasonable.
@@GregsAirplanesandAutomobiles Thanks for the help! My basic thought was that the induced drag in the drag chart had to be caused by the aircraft being at some AoA, but I didn't realize that level flight doesn't necessarily mean a level aircraft. Thanks again for clearing that up and for the Fw190 glide speed.
21:02 I don't quite understand this part. Isn't it wrong to say that the speed of the airplane counts as the true velocity? Shouldn't it be the speed at which the air moves through the jet engine? Because what does it change in terms of horse power if the platform is moving? A running engine on a car can produce a lot of hp, even when standing (in this case if the gear box isn't attached to the wheels or the engine). Its the same case - combustion and jet engine are working, they are producing power. While the combustion engine moves a crankshaft, the jet engine moves air. Where is the difference?
21:52 This is confusing me as well. If you would put a simple yet strong fan at the exhaust of a jet engine, it would obviously start turning. Connected to a crankshaft it would provide horse power (but only then!), which is illogical to my understanding.
I know it's confusing, that's why I posted the pages from Aerodynamics for Naval Aviators. So you can get a free copy and read it all for yourself. Yes, a jet engine moves air, but that's thrust, not horsepower, they are two different things.
When your car is standing it does not produce any power. But it produces a lots of torque. Once your car is accelerating, due to this torque, RPMs on your engine increase and than the engine produces power. This since power is the product of torque and RPMs. So the power of your engine is rated at a certain RPM (at the maximum power produced). At all other RPMs power is lesser !
For a linear system torque is equivalent force/thrust and RPM is equivalent to speed. By this, as Greg mentioned, with constant thrust the produced power increases with rising speed.
But Greg is certainly able to explain it much better.
Does thrust compensate for weight or mass?
neither.
So for the equation that was given at 13:00 assuming a 9,000 lb empty weight plus pilots then the 180 best glide speed is for a P-80 (or T-33) weighing about 13,000 lbs.
I agree, good job.
do any companies manufacture kit me-262s with modern engines? it seems like it was a solid enough airframe design. two engines makes it pretty safe. would Swallows still be too expensive to build today using modern shortcuts like 3D printing?
There is an near exact replica being built, it's almost ready to fly.
Love this channel: thank you so much!
It has always seemed to me that, ''lift'', isn't a good adjective in describing how an airfoil or wing actually works.
semi OT request. Could you make a video where you explain the importance of acceleration? I hear always "top speed here and top speed there", but if I need 2 years to reach my top speed, is not going to work.
I would assume that the climb rate is a sort of acceleration diagram, because without climb speed (of any type) one can also forget to accelerate at level flight, But I am unsure about that.
I would imagine that acceleration would help to get away from a bad position while not going in a straight line (otherwise the opponent can still try to land a couple of shots), thus I think it is important.
Curious as to the possible performance of the "Me262 project" reproductions built by former Boeing engineers in the early 2000's, as they had modern engines with slightly more thrust. based on your charts, they should approach Mach numbers of somewhere around 0.90. of course, i'm not a mathematician lol.
The Mach limitation is based on the wing, not the thrust, which is why it's a limit in a dive.
I can't help thinking that the German engineers had - and have - an easier life using the metric system (except km/h for speed).
awesome, thank you
Have noticed when me262 Leading edge slots open in hard turns?
What would be the maximum overall prop load on a P-51D at full power and accelerating from the specific lower speed producing the highest short-term load ? (Of course such a load would not be continuous)
Dude... i watched the whole video and I still don't get why jets have so much faster best-climb speeds than propeller airplanes. Yes I get it that jets are just faster period. However let's take a slow jet, Bell Aircomet, and compare to a fast prop plane, P-51D. The P-51 is faster than the jet at most altitudes. But the Aircomet still has a much faster best-climb speed than the Mustang?
It's a tough concept to get. If my video didn't do it, then check out Adam the Engineerd's channel, he probably has a video on this. Also you can pick up a copy of AFNA. I can't really cover this in the comments any more than whats in the video. There is just too much.