How Much Systems Knowledge Do We Need?

Roger Wilco

Roger Wilco

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A recent conversation about the secret life of controllable-pitch propeller systems has me wondering: How much knowledge about of the inner workings of aircraft systems and components does a pilot actually need? Using propeller systems as an example, do we really need to know about flyweights, speeder springs, servo pistons, etc.? Or could we fly just as safely and efficiently if we believed that the blue knob was somehow connected to a pint-size chamber inhabited by a magic elf who cranked the mechanism into compliance with our demands?
 
Roger Wilco said:
A recent conversation about the secret life of controllable-pitch propeller systems has me wondering: How much knowledge about of the inner workings of aircraft systems and components does a pilot actually need? Using propeller systems as an example, do we really need to know about flyweights, speeder springs, servo pistons, etc.? Or could we fly just as safely and efficiently if we believed that the blue knob was somehow connected to a pint-size chamber inhabited by a magic elf who cranked the mechanism into compliance with our demands?
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Enough to understand the potential failure modes and the indications of whether or not the system is operating properly.

Keep in mind that “what we need to know as pilots” has evolved over the years, and some instructors/examiners still require more systems knowledge than others.
 
Very good question. It kinda depends on YOU. How much to do you need to operate it well?

My daughter, none. She has perfect checklistedness… no understanding required, or desired…

Me, I can’t read a digital watch without understanding how an escape mechanism works…. (Footnote)

Which takes us to level B… how comprehensive are the checklists for your operations? Not comprehensive, gonna need more than less.

*Highlighting the point you don’t always need to ACTUALLY KNOW what’s going on. System knowledge helps you understand and operate better, or may be required to handle malfunctions and abnormalities. The goal isn’t to repair it while flying, but rather, land safely.
 
When everything works as it should and you don’t really need to do anything special, like get the best performance or economy from your machinery, you don’t really NEED to know all that much.

When something isn’t working quite right, you really want to know a lot more.
 
Tools said:
Which takes us to level B… how comprehensive are the checklists for your operations? Not comprehensive, gonna need more than less.
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Over the years, I would estimate that about half of the malfunctions I’ve had in airplanes actually had a checklist.

Most of the malfunctions didn’t really constitute emergencies, but…

I had a glider student ask, “how come I’ve got the stick full left and we’re not rolling?” No checklist. Knowing that his controls were connected to mine, and mine were connected to the flight control surfaces, it made sense that I could fly it when he couldn’t. But also knowing that it was pushrods and bellcranks, I used minimal control input so hopefully a loose control rod wouldn’t drop behind a bulkhead and jam the controls. (Fortunately a bellcrank broke, and no control rod ends were loose.)

I had an over voltage light in a 172. The checklist said to cycle the Master Switch off and then on. I switched it off and on, and got electrical smoke. Had to fly home with no electrical power, no flap landing, all of that good stuff. The avionics guy who fixed the radios and lights that I cooked gave me some systems knowledge…I should have only cycled the alternator side of the master switch, and left the battery online, that way the battery could act as an electrical shock absorber for the high voltage spike, and I wouldn’t have gotten smoke.

When I give checkrides in a jet, most of the systems assessment revolves around accomplishing checklists. What knob/switch/lever/handle do you move for each step, what do you expect to see happen, and how do you know if it’s doing what it’s supposed to. Sounds pretty simple on the surface, but without a solid understanding of the systems, a lot of people would be inclined to do the wrong thing and make life difficult for themselves. But quite frankly, a lot of it also revolves around the actual meaning of the words in the checklist…for a GENERATOR OFF annunciation, the checklist says Voltage….DETERMINE MALFUNCTIONING GENERATOR. It very clearly says voltage, but most people default to the ammeter or the annunciation to try to determine which generator is bad, which can very easily lead them to troubleshoot the wrong one.
 
I'm reminded of my cars many years ago... back in the day when they were far less reliable than they are today. I used to do pretty much 99.9% of the wrenching on them. In doing so I learned all the inner workings, as well as kept an eye on things...while I was under the car waiting for the oil to drain, I'd be looking and poking around

I can think of at least four major failures that happened over those years when I knew exactly what the problem was before the car coasted to a stop on teh shoulder of the road.... and in a couple cases since I knew what was happening and fully understood it, I was able to make good choicesa bout continuing on the trip vs finding the nearest autoparts store vs pulling off the road and stopping now.

Did I need that knowledge to be a "good driver"? Absolutely NO.
but without that knowledge I'd have been standing on the side of the road, scratching my head, wondering where the nearest payphone was... Instead of altering what I was doing to be safe and and continuing when appropriate.
 
If you know a lot about your airplane you are probably less likely to blindly do something stupid to make it worse. Some scenarios will appear that aren’t in a checklist. But, how much to know is really subjective. I’ve always enjoyed knowing my airplane and it’s made dealing with abnormals a bit easier and less stressful.
 
I'm in the "the more you know, the safer you are" camp.
Yes, you don't need to know how a magneto works, besides "if it's on, it makes the engine go". But if you know more, you can diagnose a failure before it becomes an emergency.
Same with alternators.
If you know what an accelerator pump is and how it works, you could attempt to use that to keep the engine running if the main carb jet got clogged.
If you know how a trim system works, you could use it to control pitch if your elevator gets stuck.
If you know how a transponder reports altitude and from where it gets that altitude information, you won't rely on it when your main altitude is not working, flying your perfectly good 757 into the ocean - see https://en.wikipedia.org/wiki/Aeroperú_Flight_603
 
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I’m 1000% in the “know every part of the system” camp. It’s not for the 9999 times that go right, it’s for that 1 time things are going bad. That is when the difference of having a complete knowledge of all the systems and being excellent at following the check list of normal operations really show different outcomes.
 
Roger Wilco said:
A recent conversation about the secret life of controllable-pitch propeller systems has me wondering: How much knowledge about of the inner workings of aircraft systems and components does a pilot actually need? Using propeller systems as an example, do we really need to know about flyweights, speeder springs, servo pistons, etc.? Or could we fly just as safely and efficiently if we believed that the blue knob was somehow connected to a pint-size chamber inhabited by a magic elf who cranked the mechanism into compliance with our demands?
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Ah, the mention of speeder springs is good for a long time ago flash back. After UPT some of us were assigned to C-130s. When we were in systems class it was deer in the headlight time once the instructors started in on the props. All of us new pilots were just looking at each other with out a clue of what they were talking about. Move forward in time just a little bit, now I'm flying as a copilot between Thailand and Cambodia and the aircraft commander, a crusty "old" major, is getting an line check by a young captain. The examiner had been quizzing the major for some time and it was obvious the major was becoming just a little annoyed. Finally the captain asks how do the props work. The short reply: PFM. PFM the captain asks? Pure F***ing Magic was the answer in a rather exasperated tone. There were no more questions for the rest of the flight.
 
Roger Wilco said:
A recent conversation about the secret life of controllable-pitch propeller systems has me wondering: How much knowledge about of the inner workings of aircraft systems and components does a pilot actually need? Using propeller systems as an example, do we really need to know about flyweights, speeder springs, servo pistons, etc.? Or could we fly just as safely and efficiently if we believed that the blue knob was somehow connected to a pint-size chamber inhabited by a magic elf who cranked the mechanism into compliance with our demands?
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I hope this is a joke.
 
You can absolutely fly VERY advanced jets without knowing squat about them. The Airbus is a great example. They don’t even tell you stuff you SHOULD know…

Yet they fly all the time successfully. It’s automated to the point you ain’t gonna be able to do much anyway….

Turns out the thing has a gas tank in the vertical stab. Not a single switch or control for it… nada.

My inner grumpy old guy says this is bad… but.. but.. I ain’t gotta lot to use against this advance in technology. Pretty sure who I consider old guys thought the exact same thing, yet here we are.

Used to have to be able to take apart your model T engine every so often to clean it! Take the whole damn motor apart, clean it, reassemble and press on… now we don’t even change the spark plugs or grease the chassis.

For your normal 30s technology 1980s plane, know everything. But this too shall pass.
 
Tools said:
Used to have to be able to take apart your model T engine every so often to clean it! Take the whole damn motor apart, clean it, reassemble and press on…
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You don’t still disassemble your cars engine, inspect, hone your cylinders and replace your piston rings, lap your valves and do a full kerosene flush of the oil galleries every fall? … darn kids these days, no wonder the world has moved towards disposable items, nobody takes the time to do the proper maintenance to make things last ;)
 
Roger Wilco said:
A recent conversation about the secret life of controllable-pitch propeller systems has me wondering: How much knowledge about of the inner workings of aircraft systems and components does a pilot actually need? Using propeller systems as an example, do we really need to know about flyweights, speeder springs, servo pistons, etc.? Or could we fly just as safely and efficiently if we believed that the blue knob was somehow connected to a pint-size chamber inhabited by a magic elf who cranked the mechanism into compliance with our demands?
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I have heard this question a few times in the past " How much knowledge about of the inner workings of aircraft systems and components does a pilot actually need? " and wondered how do you explain the "WHY" to someone who may not have any bases for understanding. Because pilots / plane owners have a myriad of reasons for being a pilot / airplane owner. What's the "mission" ?, a commute, to visit family & friends that are more than a 30 or 40 minute drive, to get from point A to point B quicker than driving. Also, for the commercial group, a "PAYCHECK" and bragging rights that go with it! Then! there is those (not just crtf'd pilots) who look up when an aircraft goes overhead and watch seagulls and ravens etc and recognize the similarities in how they utilize the atmosphere. That may be to much for some people who just need to know where to put the gas in and what auto shop to drop off for an oil change (because the engine light told them to).This group, gets into their cars and turn the key and go. If the car gets hot or just stops, they don't have to worry, just pull over to the curb and call triple "A" and a uber. In an airplane "YOU CAN'T JUST PULL OVER TO THE SIDE OF THE ROAD !".
Granted ! depending on the complexity of the aircraft, a basic understanding of the the systems and how they operate is essential for safety! Again the degree of understanding necessary depends on the complexity of the aircraft.
As an example using a recip scenario (i am sure there are similar scenarios with turbine engines); pilots bring spark plugs to be cleaned because their run ups were not satisfactory; plugs cleaned and pilot instructed: lean during idle / taxi , what ends up happening is the pilot retinuely pulls the mxt control about a half an inch or whatever he feels is right, that same measurement every time /day he flys ! without understanding what he is doing beyond pulling the mxtr control, and without further understanding, at least that the atmosphere is changing from airport to airport and day to day or the effect it all has on how the fuel / air xtr is being proportioned and how this not only helps keep spark plugs clean but affects performance and fuel economy at cruse as well !
I am not an instructor, just a pilot (well, a ap too), I am a firm believer, the more you know / understand your steed, the safer you are.
 
The more letters on your certificate(s) and endorsement(s), the more systems knowledge you need to meet the regulatory minimum.

To quote someone around here, don’t accept the minimum.
 
Daleandee said:
I recall trying to explain to an ex-girlfriend how that sometimes when a car is overheating it might help a bit to turn on the heater. Didn't go well ...
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Reminds me of a story from my Army days. I was riding in a HMMWV one cold night in a training area in Japan. "Dang Sir" the driver said, "the heater is broke. It was blowing hot air and now it blows cold air."

I thought about that for a moment and told him to shut off the engine quickly. Popped the hood and sure enough, we had ruptured a coolant hose. We had to be close to seizing that engine.
 
Ed Haywood said:
Reminds me of a story from my Army days. I was riding in a HMMWV one cold night in a training area in Japan. "Dang Sir" the driver said, "the heater is broke. It was blowing hot air and now it blows cold air."

I thought about that for a moment and told him to shut off the engine quickly. Popped the hood and sure enough, we had ruptured a coolant hose. We had to be close to seizing that engine.
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Funny. At the end of Noble Anvil we were convoying back to Germany and my shotgun said “Dang, engine’s getting hot”. It’s June in southern Europe and I put the heater to high. We limp into Marseille and figure out we blew a head gasket on the M923.

Got that hooked up and spent the next two days getting back to Germany as pax in a HMMWV. Overall, a spending the last 1/3 if a six day convoy as pax didn’t suck as much as I thought it would. I still have a Stars & Stripes Europe edition with our return to Spang on the front page.
 
I don't think knowing the systems in depth is of great value. A general understanding and being able to run the system checklist (if you have one) for the condition you are experiencing is enough.

Your engine sputters/runs rough most POH have you do some very basic checks and advise to get on the ground ASAP.

So what if you know the oil pressure relief valve spring compression value... oil pressure low land. You may know how a govenor works but when a seal on the prop hub lets out all the oil you ain't fixing it until you land.
 
For the typical loop I see around here, which is: fly -> squawk -> throw plane and checkbook at shop, I would say zero knowledge is needed.

If one wishes to describe a problem accurately, intelligently, and pre-narrowed to one's mechanic, and try to whittle the prospective bill down from tens of thou to mere hundreds or low thousands -- system knowledge helps. But yeah, to OP's magical elf point, it's optional. :D
 
One should understand their systems to the extent that they have power to use them.
Anything more is a hobby unless you are paid to fix it.


6PC,
Who typed this on a XenForo forum having never seen the code that translates my thoughts into provocative text by means of button pushes on a device that is in no way touching my thoughts or XenForo.
 
My proudest moment as a student was hearing an exhaust leak during run up. Initially blamed it on new headsets. The slightest difference. Extra mag check was good. Instructor didn't hear it. Firewalled throttle. Nah, it ain't right. Aborting takeoff. High speed taxi and work throttle until instructor heard it. He asked what I thought it was. I think out loud. I think it's an exhaust leak, but it would be on helluva exhaust leak. So maybe running on 3 cylinders. But the mag check was good, and it has power and not running rough. Just sounds terrible. I'm going exhaust leak. Plane didn't have egt's to diagnose

Uncowl. Inner exhaust stud missing, outer nut fell off. Instructor was impressed by my diagnostics. Extra checklist item added to preflight.
 
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I have to admit I get a chuckle when a pilot or even CFI can regurgitate, through rote memorization, some arcane facts, but have zero knowledge beyond it.

Knowing how a constant speed prop works should help with the “magic “ someone commented on above; especially the failure modes.
 
DaleB said:
When something isn’t working quite right, you really want to know a lot more.
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Sure. But even then, enough to troubleshoot and potentially fix from your seat in the airplane. I was going to make something up about adding oil in flight, but I don’t have to. I was once with a CFI who said that if the landing gear on a Cutlass gets stuck half way down when extending it, open the door and jump on it.
 
Initial Fix said:
I have to admit I get a chuckle when a pilot or even CFI can regurgitate, through rote memorization, some arcane facts, but have zero knowledge beyond it.

Knowing how a constant speed prop works should help with the “magic “ someone commented on above; especially the failure modes.
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Ever watch a pilot constantly and unnecessarily adjusting the prop in flight? Those can usually spit out that rote stuff.

When I do transitions to constant speed props, I reference one or two videos I think do a decent job of describing their inner workings. That’s intended as an overview. From there, they can go as deep or shallow as they want. My job is to demystify it for practical operation in normal flight and emergencies.
 
Tools said:
Used to have to be able to take apart your model T engine every so often to clean it! Take the whole damn motor apart, clean it, reassemble and press on… now we don’t even change the spark plugs or grease the chassis.
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It used to be the car owner's manual told you how to set the valves. Nowadays it warns you not to drink the battery acid. :dunno:
 
I’m reminded of a couple of instances where additional systems knowledge would have been good in the last few years…

An air conditioning system improperly MEL’d by pulling the wrong CB (back to that “reading” thing), combined with a fairly common heat duct problem that was unrecognized, combined with improper operation of the environmental system resulting in excessive heat in the cabin and environmental smoke that the checklist couldn’t resolve.

Thrust reversers MEL’d because they didn’t deploy on landing, and the next landing required the use of emergency brakes because the problem wasn’t the thrust reversers.
 
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Roger Wilco said:
A recent conversation about the secret life of controllable-pitch propeller systems has me wondering: How much knowledge about of the inner workings of aircraft systems and components does a pilot actually need? Using propeller systems as an example, do we really need to know about flyweights, speeder springs, servo pistons, etc.? Or could we fly just as safely and efficiently if we believed that the blue knob was somehow connected to a pint-size chamber inhabited by a magic elf who cranked the mechanism into compliance with our demands?
Click to expand...
Simple answer: learn the required POH materials for the systems, then continue your learning until marginal cost exceeds marginal return.

Using your example: Getting your PhD in constant speed propeller design will not materially impact your ability to operate one.
 
A perfect example of a lack of knowledge becoming a tragedy, the 737 Max MCAS system.

On the other hand, I once had a pilot come to me wanting a high performance endorsement. He spent a month or more self learning about constant speed propellers, and by the time he came to me to fly had worked himself into an absolute fit about being able to operate one. We started off in the classroom, where I tried to explain some of his misconceptions but he didn't believe me. Then we went flying. After the flight, he remarked, "THAT'S IT?"
 
Strong speculation on another board is that this accident is systems-knowledge related…

Kenny Phillips

Thread 'King Air Fatal, Coral Springs, Hurricane Relief Flight, 11/10/25'

Carrying supplies to Jamaica for Hurricane Melissa relief.

www.nbcmiami.com

2 dead after small plane heading to Jamaica for hurricane relief crashes in Coral Springs

Authorities were searching for possible survivors after a small plane that was bringing hurricane relief supplies to Jamaica crashed in a lake in a Coral Springs neighborhood on Monday morning, officials said.
www.nbcmiami.com www.nbcmiami.com
 
So the illusion is, everything provided to you in systems manuals and emergency checklists is 100% complete and will accommodate all failures and potential safety risks? It's not!

Flight Safety used to train "paths of influence" in their troubleshooting course (1999-2000). I like to understand what I call system partitioning.
 
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