Homebuilder here. I've been flying the RV9A that I built for 5 years. This conversation was a good one and I completely agree that homebuilders have this right. I get asked why I would ever fly something I built in my garage and my answer is "because I know every rivet, every inch of this plane" and "why would I want to fly a flight school Cessna that I know nothing about its maintenance history". It's the difference between flying on confidence and flying on hope.
Absolutely. Except... I am not mechanically inclined, so I would not have confidence in a plane I built. I do want to understand it as much as I can, though. - Martin
This is awesome, I am a sub 100 hour private pilot from Canada and I think it is our due diligence to know as much about how airplanes work as possible. I think Doug is so knowledgeable and I would love to have the opportunity to learn more about airplanes from you guys on this channel
Thanks, Kev. You can already find a few more videos with Doug here (multi engine, tail dragger, Vg diagram, electrical system, etc.), and we'll make more in the future. - Martin
+1 on learning more AND reading the Maintenance Manual. You never know when some gremlin might pop up in-flight and a DETAILED understanding what's going on makes all the difference. I had a mechanical issue w/angry lights during my first solo. I had read through the MM and remembered the chapter on this, understood what was happening, and knew it wasn't going to pose an issue for the flight.
Nice video Doug and Martin. When I started flying my 210 "Lola", I was extremely weak on systems and how it works so I can work the plane.... just recently I've started doing maintenance on Lola with my A&P/IA over my shoulder. I've gotten an AMT logbook and log the hours now.
Well-done, gentlemen. Thank you. As far as I’m aware, only Cirrus and Diamond are commercially considered 21st century products. The vast majority of the iron we train with, use, and repair is decades old. Having a working knowledge of why these birds do what they do, the way they do it, goes a long way to quickly and efficiently determining how to safely make one takeoff equal one landing, on-purpose, every time.
I don't know the Diamond, but I am quite familiar with the Cirrus piston airplanes. Their systems are quite a bit more complex than, say, a single-engine Cessna, Piper or Beechcraft. But even Cirrus in their official flight training programs (which are quite good, actually) teach about those systems - how they work, and how failures can be diagnosed based on that knowledge. Regards, Martin
I wish I could do maintenance on my Bonanza - I am not all that mechanically inclined. What I strive for is a good understanding of my aircraft systems, not so much the ability to repair something myself when it's broken. But I guess the former is needed to do the latter. - Martin
Doug's comment about precision versus accuracy can't be overstated... they are very often not the same thing in the real world. In addition to reviewing the maintenance manual, an owner assisted annual is a tremendous opportunity learn about your aircraft.
Absolutely correct. Knowledge is power. The power to make good decisions instead of guessing. There are an untold number of pilots and passengers that are dead that should be alive, just because the pilots didn't see the need to gain knowledge. Thanks, guys!
I've learned a lot just hanging around the hangar while our A&P is working on our club plane. Seeing some of the systems "uncovered" and through a differently trained eye has been amazingly educational.
Excellent, Martin & Doug! It's such a joy to be able to understand the workings of a flying machine, and essential to be genuinely interested in learing about it if you're a pilot.
Great video Martin! Recently got back from sim school for the Cessna CJ with a coworker. The instructors were adamant that we should not be trying to draw system diagrams yet wanted us to memorize pages and pages of system “what ifs”. My coworker almost wants nuts memorizing until we sat down and talked through drawing out systems. After that she had no problem, could figure her way through any question, and aced the oral. We need to bring back this sort of knowledge yet I’m afraid it’s too late for the industry as a whole.
Sounds like those instructors were completely of the "work the airplane" kind, maybe because they themselves did not had a good understanding of the aircraft systems? (I am just speculating, of course, but it would explain the attitude.). Good on her for digging deeper, which in the end made her life much easier from what you wrote. - Martin
@@martinpauly The instructors had a good grasp of the airplane and taught well but didn’t expect enough IMO from us. At the GA level at least I think an expanded level of systems knowledge will always be for those who want to go above and beyond the minimum standards and not the masses. It would take a grassroots effort, like the creation of the ACS, to get more systems knowledge into the initial certificates. Flight instructors need to be dragged into the maintenance shops and the manuals but that seems like a long shot to me.
That's certainly an extreme example - one which very few people can achieve, but which all pilots should WANT to be able to achieve. As long as we stay curious and keep learning, we are on a good trajectory, - Martin
Another excellent video with Doug. Very true and valuable content for any aviator! For me, flying and mechanicing has always come hand in hand. I’m a CFI and recently got my A&P mechanic certification as well. This video was a great reminder that I need to be that CFI/ A&P that shows students and aircraft owners “under the hood” of the aircraft.
Another great episode, really helpful for me as a "digital native" flight student, to know that behind the fancy digital gauges, it is still same good old mechanics from centuries ago. I will definitely start learning from the maintenance manual, even if it's from a different SE plane, should be better than nothing I think. Thank you both!!!
I Totally agree with Doug! In the cockpit environment of "Digital Saturation" We pilots of our own aircraft or rental aircraft Must make it our business to learn all we can about the installed systems of the Airplane you are flying! All the data in the world doesn't mean anything to you if you don't Know how to analyze and decipher it for your use.
Great interview! And an excellent point! Love the idea of reviewing the maintenance manual. Reminds me when when I was a kid and would read Haynes manuals for fun.
Excellent, thank you! Here is another motivation to learn about all systems: it can save you money when you can help figure out the source of an issue, if it means not replacing completely an avionics component or other parts. As PIC and owners, we know the planes and spend more time on them than others, we could be a useful source of diagnosis.
Great video. I have seen a trend recently where pilots are chastised for wanting to dig deeper. 'Leave that to the professionals (mechanics). You just fly the airplane' is said far too often, even within small GA pilots. I think that is a copout, from people who simply have no mechanical skills.
I can understand why someone doesn't want to work on their airplane (I count myself in that camp). But that's not the same as not wanting to understand how it works. Meaning you can have it both: leave the work to the mechanics if you like, but we should all seek to have an understanding of our aircraft. - Martin
Doug reminds me of my primary flight instructor … other than Doug seems a long nicer. 😁. Their level or knowledge and skill are very similar as is their philosophy. R. C. “Dick” Johnston was a great instructor.
Great video 5:25. Could you elaborate. Aren't there plenty of metals that are capable of withstanding 1500 °F and not melt? (Sure, CHT 1500 would indicate a bad day, but in the context of systems knowledge or metallurgy, the argument didn't quite convince me). On the plus side, I think I detect that people are getting to be conscious to "the computer is not always right", which is a good thing, in the sense that it alleviates the very real problem that you mentioned that humans tend to confuse great precision with great reliability. Back when GPS was new, and traditional radio navigation only so reliable, initially most people would be such in awe of the incredible precision that they would believe it over every other instrument (and of course, the majority of the time you can do that, and you will be 'correct'). I think people nowadays are getting to the point where they might look out the window and simply conclude "that position on the GPS, that is not where I am at" (maybe the computer froze and shows an outdated position), or a perhaps more realistic scenario, if the moving map waypoint doesn't seem to match up with your chart or approach plate I think pilots nowadays more readily will suspect the navigator waypoint could be off.
Aluminum melts somewhere around 1200 ºF - or maybe Doug meant Celsius, not Fahrenheit? Either way, as you said: a CHT of 1500 would be a really bad. Are we getting better at questioning digitally presented information? Maybe (we are learning!!!), but I plenty of people get worked up about precise numbers when something approximate is all that's needed. Regards, Martin
@@B25Flyer Yups, that all makes sense. When I first watched the interview I was just caught off guard that a random comment about engine CHT from the internet would automatically refer to aluminum cylinder heads. Rewatching it, I now understand it was implied in the context. Thank you for answering. Great video.
Someone reporting a CHT of 1500F is probably mistaking it for the EGT reading. Lack of a “sanity check” implies a misunderstanding of how the engine itself, or the engine monitoring system, operates.
LOL! I wasn't even thinking about that! Of course! LOL I was up late watching the progress of my dad's flight. Turns out he was on a Dreamliner, but not heading to Tahiti... Southern Africa, as I previously mentioned. So where will you be heading next Martin?@@martinpauly
Hi Martin Doug said that higher MAP is stressing our engine but watching all of Mike Bush's videos he suggested that higher MAP to RPM truly dose not matter and suggest it is wise to run our IO520 and IO550 that way . IE my IO520. at 27MP and RPM 2100 LOP . Any thoughts you have on this as I know you are a LOP advocate. Also Bob Ripley says the same thing that Higher MP isn't hurting our engines.
High M.P. with low fuel flow (low power) is fine. High M.P. with low rpm at take-off fuel flow (high power) can be harmful and cause detonation. You are making our point about understanding how it works, not just how to work it.
Mick, look at your first sentence again, and you will see that it's not an apples-to-apples comparison: "higher MAP" on the one hand, and "higher MAP to RPM" on the other hand. Those are different things. Let's look at them both: High manifold pressure (MP): Each engine will have limits for MP, which you can find in the POH and the engine documentation. The limits might be time-bound (e.g. "MP > 30 inches for no more than 5 minutes"), and they might be tied to RPM. In general, you don't want to have. combination of very high power (to which MP is a contributor, but not the only one) and very low RPM - that would be like driving a car uphill in high gear. MP vs. RPM relationship: MP is measured in inches of mercury. RPM is measured in 1/min. They are different units, they measure completely different things, and the mere numbers are typically magnitudes apart (e.g. 22" of MP, 2500 RPM). To proclaim one number divided by 100 should never exceed the other number or your engine will be destroyed is just ludicrous. So Mike Busch is stating the obvious. Putting the two together, we can conclude: - It is OK to run an engine "oversquare" (e.g. 25" MP at 2300 RPM) - Running at high power and low RPM should be avoided Again, consult your POH for details on YOUR aircraft, because the generic guidance above needs to be augmented with actual numbers and limits for your engine and your airframe. Regards, Martin
@@martinpauly Thank you Martin for your input on this I actually still only run Squared just cant convince myself to put undo pressure on my engine and I dont have to to get there that fast. I truly love the flight! And my bonanza!!!!!!
I agree with both of you 100% My Grand-kids couldn't change a spark plug, find it, or know what it was. Much less leave the computer game long enough to find out. I graduated HS in 1970. At my job I went to school nights to get my degree. I made supervisor of an IT team fast, then I went to night school 2 days a week for 30 years to keep up! I also totally restored my 1978 BMW R100RS motorcycle after riding it 300k miles. The 1 thing, beside flying, I made time for. These days there is a severe inability to figure things out. Even if they can "Google it" they can't follow simple directions. I'm afraid to fly commercial these days. Their not former military pilots up front anymore, they are kids flying computer games. But instead of reset when things go bad.... well you know that I mean. Scary ... 8( --gary
Gary, we can all see the symptoms you describe - sometimes more, sometimes less, depending on where you look. And there are of course exceptions, too - some very talented and smart young people, eager to learn and explore the world. Like you, I wish we'd see more of that spirit these days. - Martin
I agree with Doug 1000% having been a pilot for over 50 years retired now from 121 and corporate world. In the early years we had to know at lot more information about the airplane especially with transport category airplanes compared to what pilots need to know today. As an example the pilots had to know on the B 727 the fuel pumps on the essential buss where the pumps in wing front left ie Seattle right wing in the aft ie Miami. That is with the airplane oriented to the north. The first airplane that I flew that had an APU I could tell you the manufacturer of the APU and its limitations. Later in life I was an Instructor on the B777 every instructor I asked could not tell me who manufactured the APU. I had to go digging to find out. 😀🛫 It is nice to see two other Beech Talkers!
Homebuilder here. I've been flying the RV9A that I built for 5 years. This conversation was a good one and I completely agree that homebuilders have this right. I get asked why I would ever fly something I built in my garage and my answer is "because I know every rivet, every inch of this plane" and "why would I want to fly a flight school Cessna that I know nothing about its maintenance history". It's the difference between flying on confidence and flying on hope.
Absolutely. Except... I am not mechanically inclined, so I would not have confidence in a plane I built. I do want to understand it as much as I can, though.
- Martin
This is awesome, I am a sub 100 hour private pilot from Canada and I think it is our due diligence to know as much about how airplanes work as possible. I think Doug is so knowledgeable and I would love to have the opportunity to learn more about airplanes from you guys on this channel
Thanks, Kev. You can already find a few more videos with Doug here (multi engine, tail dragger, Vg diagram, electrical system, etc.), and we'll make more in the future.
- Martin
+1 on learning more AND reading the Maintenance Manual. You never know when some gremlin might pop up in-flight and a DETAILED understanding what's going on makes all the difference. I had a mechanical issue w/angry lights during my first solo. I had read through the MM and remembered the chapter on this, understood what was happening, and knew it wasn't going to pose an issue for the flight.
Good on you!
- Martin
Nice video Doug and Martin. When I started flying my 210 "Lola", I was extremely weak on systems and how it works so I can work the plane.... just recently I've started doing maintenance on Lola with my A&P/IA over my shoulder. I've gotten an AMT logbook and log the hours now.
Good on you, Dan 👍
Well-done, gentlemen. Thank you. As far as I’m aware, only Cirrus and Diamond are commercially considered 21st century products. The vast majority of the iron we train with, use, and repair is decades old. Having a working knowledge of why these birds do what they do, the way they do it, goes a long way to quickly and efficiently determining how to safely make one takeoff equal one landing, on-purpose, every time.
I don't know the Diamond, but I am quite familiar with the Cirrus piston airplanes. Their systems are quite a bit more complex than, say, a single-engine Cessna, Piper or Beechcraft. But even Cirrus in their official flight training programs (which are quite good, actually) teach about those systems - how they work, and how failures can be diagnosed based on that knowledge.
Regards,
Martin
Yes please do more maintenance related videos
I wish I could do maintenance on my Bonanza - I am not all that mechanically inclined. What I strive for is a good understanding of my aircraft systems, not so much the ability to repair something myself when it's broken. But I guess the former is needed to do the latter.
- Martin
Doug's comment about precision versus accuracy can't be overstated... they are very often not the same thing in the real world. In addition to reviewing the maintenance manual, an owner assisted annual is a tremendous opportunity learn about your aircraft.
Yes! Doug & Martin are back dropping the systems knowledge. Please keep sharing the systems knowledge.
An insatiable quest for knowledge. Amen!
"Insatiable knowledge" is what we all should say in addition to "license to learn".
- Martin
@@martinpauly exactly 💯
wow! excellent eye opener discussion. thanks for sharing Doug's wisdom!
Glad you enjoyed it!
- Martin
Absolutely correct. Knowledge is power. The power to make good decisions instead of guessing.
There are an untold number of pilots and passengers that are dead that should be alive, just because the pilots didn't see the need to gain knowledge.
Thanks, guys!
It's sad but correct, yes.
- Martin
I've learned a lot just hanging around the hangar while our A&P is working on our club plane. Seeing some of the systems "uncovered" and through a differently trained eye has been amazingly educational.
Absolutely!
- Martin
I could listen to Doug for hours - thank you Martin for these wonderful videos!
Magnificent discussion, i enjoyed it so much thanks a lot Captain, well done .
Thanks - glad you found this meaningful.
- Martin
Thanks for sharing
Excellent, Martin & Doug! It's such a joy to be able to understand the workings of a flying machine, and essential to be genuinely interested in learing about it if you're a pilot.
Thanks for the kind feedback, Frans - and nice to hear from you!
Greetings from Iowa!
- Martin
Great video and topic. I wish videos like this got 1 million views!
That would be nice, but I don't think it'll happen.
- Martin
Great video Martin! Recently got back from sim school for the Cessna CJ with a coworker. The instructors were adamant that we should not be trying to draw system diagrams yet wanted us to memorize pages and pages of system “what ifs”. My coworker almost wants nuts memorizing until we sat down and talked through drawing out systems. After that she had no problem, could figure her way through any question, and aced the oral. We need to bring back this sort of knowledge yet I’m afraid it’s too late for the industry as a whole.
It might be too late for the jet drivers, but those of us hauling our friends and families in a Baron or Bo can, and should, do better. Doug Rozendaal
Sounds like those instructors were completely of the "work the airplane" kind, maybe because they themselves did not had a good understanding of the aircraft systems? (I am just speculating, of course, but it would explain the attitude.). Good on her for digging deeper, which in the end made her life much easier from what you wrote.
- Martin
@@martinpauly The instructors had a good grasp of the airplane and taught well but didn’t expect enough IMO from us. At the GA level at least I think an expanded level of systems knowledge will always be for those who want to go above and beyond the minimum standards and not the masses. It would take a grassroots effort, like the creation of the ACS, to get more systems knowledge into the initial certificates. Flight instructors need to be dragged into the maintenance shops and the manuals but that seems like a long shot to me.
I read Chuck Yeager's book a few years ago. In that he talks about knowing, at an engineering level, every aircraft type he flew.
That's certainly an extreme example - one which very few people can achieve, but which all pilots should WANT to be able to achieve. As long as we stay curious and keep learning, we are on a good trajectory,
- Martin
Another excellent video with Doug. Very true and valuable content for any aviator! For me, flying and mechanicing has always come hand in hand. I’m a CFI and recently got my A&P mechanic certification as well. This video was a great reminder that I need to be that CFI/ A&P that shows students and aircraft owners “under the hood” of the aircraft.
Another great episode, really helpful for me as a "digital native" flight student, to know that behind the fancy digital gauges, it is still same good old mechanics from centuries ago. I will definitely start learning from the maintenance manual, even if it's from a different SE plane, should be better than nothing I think. Thank you both!!!
Glad it was helpful!
- Martin
I love these videos. They are very informative. Thanks for sharing them.
You are welcome!
- Martin
You should consider making a podcast on topics like this! Or even bonanza specific topics. I would totally listen.
Bonanza-specific maintenance/tech topics? ABS has a bunch of them on their channel.
- Martin
@@martinpauly oh yes that’s right.
Lots of excellent points - thanks to both of you for this!
Happy to do it - glad you like it!
- Martin
I Totally agree with Doug! In the cockpit environment of "Digital Saturation" We pilots of our own aircraft or rental aircraft Must make it our business to learn all we can about the installed systems of the Airplane you are flying! All the data in the world doesn't mean anything to you if you don't Know how to analyze and decipher it for your use.
I agree!
- Martin
Great video Martin!
Glad you enjoyed it!
- Martin
Great interview! And an excellent point! Love the idea of reviewing the maintenance manual. Reminds me when when I was a kid and would read Haynes manuals for fun.
Same idea, yes, and very valuable information.
- Martin
Great video!
Thanks!
- Martin
Excellent, thank you! Here is another motivation to learn about all systems: it can save you money when you can help figure out the source of an issue, if it means not replacing completely an avionics component or other parts. As PIC and owners, we know the planes and spend more time on them than others, we could be a useful source of diagnosis.
That's absolutely correct, yes!
- Martin
Excellent and so true! Learn, learn, learn.
100% agree
Amen to this
Great video. I have seen a trend recently where pilots are chastised for wanting to dig deeper. 'Leave that to the professionals (mechanics). You just fly the airplane' is said far too often, even within small GA pilots. I think that is a copout, from people who simply have no mechanical skills.
I can understand why someone doesn't want to work on their airplane (I count myself in that camp). But that's not the same as not wanting to understand how it works. Meaning you can have it both: leave the work to the mechanics if you like, but we should all seek to have an understanding of our aircraft.
- Martin
Doug reminds me of my primary flight instructor … other than Doug seems a long nicer. 😁. Their level or knowledge and skill are very similar as is their philosophy. R. C. “Dick” Johnston was a great instructor.
Great video
5:25. Could you elaborate. Aren't there plenty of metals that are capable of withstanding 1500 °F and not melt? (Sure, CHT 1500 would indicate a bad day, but in the context of systems knowledge or metallurgy, the argument didn't quite convince me).
On the plus side, I think I detect that people are getting to be conscious to "the computer is not always right", which is a good thing, in the sense that it alleviates the very real problem that you mentioned that humans tend to confuse great precision with great reliability. Back when GPS was new, and traditional radio navigation only so reliable, initially most people would be such in awe of the incredible precision that they would believe it over every other instrument (and of course, the majority of the time you can do that, and you will be 'correct'). I think people nowadays are getting to the point where they might look out the window and simply conclude "that position on the GPS, that is not where I am at" (maybe the computer froze and shows an outdated position), or a perhaps more realistic scenario, if the moving map waypoint doesn't seem to match up with your chart or approach plate I think pilots nowadays more readily will suspect the navigator waypoint could be off.
Aluminum melts somewhere around 1200 ºF - or maybe Doug meant Celsius, not Fahrenheit? Either way, as you said: a CHT of 1500 would be a really bad.
Are we getting better at questioning digitally presented information? Maybe (we are learning!!!), but I plenty of people get worked up about precise numbers when something approximate is all that's needed.
Regards,
Martin
@@martinpauly That makes sense, that maybe Doug was referring specifically to aluminium.
The CHT measures temperature of an aluminum cylinder head. At 1500, it's a liquid
@@B25Flyer Yups, that all makes sense. When I first watched the interview I was just caught off guard that a random comment about engine CHT from the internet would automatically refer to aluminum cylinder heads. Rewatching it, I now understand it was implied in the context. Thank you for answering. Great video.
Someone reporting a CHT of 1500F is probably mistaking it for the EGT reading. Lack of a “sanity check” implies a misunderstanding of how the engine itself, or the engine monitoring system, operates.
Hmm. You sure get up early! Especially for a Saturday.
Me? I'm up late. : )
Let me fill you in on a little secret... UA-cam allows scheduling the release of a video head of time, so I don't have to set an alarm! 😎
- Martin
LOL! I wasn't even thinking about that! Of course! LOL
I was up late watching the progress of my dad's flight. Turns out he was on a Dreamliner, but not heading to Tahiti... Southern Africa, as I previously mentioned. So where will you be heading next Martin?@@martinpauly
@@Cousin. Next up is the BeechTalk fly-in in Knoxville, TN - first weekend in October
Sounds like fun! I don't think I'll be at any events outside CA or OR until next year. Hopefully then!@@martinpauly
Hi Martin Doug said that higher MAP is stressing our engine but watching all of Mike Bush's videos he suggested that higher MAP to RPM truly dose not matter and suggest it is wise to run our IO520 and IO550 that way . IE my IO520. at 27MP and RPM 2100 LOP . Any thoughts you have on this as I know you are a LOP advocate. Also Bob Ripley says the same thing that Higher MP isn't hurting our engines.
High M.P. with low fuel flow (low power) is fine. High M.P. with low rpm at take-off fuel flow (high power) can be harmful and cause detonation. You are making our point about understanding how it works, not just how to work it.
Mick, look at your first sentence again, and you will see that it's not an apples-to-apples comparison: "higher MAP" on the one hand, and "higher MAP to RPM" on the other hand. Those are different things. Let's look at them both:
High manifold pressure (MP): Each engine will have limits for MP, which you can find in the POH and the engine documentation. The limits might be time-bound (e.g. "MP > 30 inches for no more than 5 minutes"), and they might be tied to RPM. In general, you don't want to have. combination of very high power (to which MP is a contributor, but not the only one) and very low RPM - that would be like driving a car uphill in high gear.
MP vs. RPM relationship: MP is measured in inches of mercury. RPM is measured in 1/min. They are different units, they measure completely different things, and the mere numbers are typically magnitudes apart (e.g. 22" of MP, 2500 RPM). To proclaim one number divided by 100 should never exceed the other number or your engine will be destroyed is just ludicrous. So Mike Busch is stating the obvious.
Putting the two together, we can conclude:
- It is OK to run an engine "oversquare" (e.g. 25" MP at 2300 RPM)
- Running at high power and low RPM should be avoided
Again, consult your POH for details on YOUR aircraft, because the generic guidance above needs to be augmented with actual numbers and limits for your engine and your airframe.
Regards,
Martin
@@martinpauly Thank you Martin for your input on this I actually still only run Squared just cant convince myself to put undo pressure on my engine and I dont have to to get there that fast. I truly love the flight! And my bonanza!!!!!!
I agree with both of you 100% My Grand-kids couldn't change a spark plug, find it, or know what it was. Much less leave the computer game long enough to find out. I graduated HS in 1970. At my job I went to school nights to get my degree. I made supervisor of an IT team fast, then I went to night school 2 days a week for 30 years to keep up! I also totally restored my 1978 BMW R100RS motorcycle after riding it 300k miles. The 1 thing, beside flying, I made time for. These days there is a severe inability to figure things out. Even if they can "Google it" they can't follow simple directions. I'm afraid to fly commercial these days. Their not former military pilots up front anymore, they are kids flying computer games. But instead of reset when things go bad.... well you know that I mean. Scary ... 8( --gary
Gary, we can all see the symptoms you describe - sometimes more, sometimes less, depending on where you look. And there are of course exceptions, too - some very talented and smart young people, eager to learn and explore the world. Like you, I wish we'd see more of that spirit these days.
- Martin
I agree with Doug 1000% having been a pilot for over 50 years retired now from 121 and corporate world. In the early years we had to know at lot more information about the airplane especially with transport category airplanes compared to what pilots need to know today.
As an example the pilots had to know on the B 727 the fuel pumps on the essential buss where the pumps in wing front left ie Seattle right wing in the aft ie Miami. That is with the airplane oriented to the north.
The first airplane that I flew that had an APU I could tell you the manufacturer of the APU and its limitations. Later in life I was an Instructor on the B777 every instructor I asked could not tell me who manufactured the APU. I had to go digging to find out. 😀🛫 It is nice to see two other Beech Talkers!