How Much Systems Knowledge Do We Need?

Carb ice is the biggest single cause of engine failure, and that's because the pilot doesn't understand the physics of carb ice. He thinks it's a wintertime-only thing, or only happens if you're flying in visible moisture like rain/cloud/mist. The power starts to drop off, so he pushes the throttle in more. Eventually, maybe, he pulls the carb heat, and the power drops further so he pushes it back in, and the ice-up continues until the engine is dead and he's forced down.

Carb ice is one of those things that can't be induced at will to demonstrate it. So the student needs to know what it's all about and the conditions conducive to it, what to do and what to expect. Anything less and he's severely handicapped.
 
Ernest K. Gann tells a story of an experience in “Fate is the Hunter” that he had while flying a DC-4. The intakes on the cowlings were icing over and the engines were being starved of air. The pilot knew enough about his engines to intentionally backfire the engines throgh the carbs to blow out the buildup of ice in the intakes. If it wasnt for that, that plane would’ve gone down for sure. Knowledge on engine operation above and beyond what the POH needed was what saved the day.
 
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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The question posed makes the standard internet error of forcing a false binary choice. No, you probably don't need advanced engineering knowledge in most cases. Yes, magic-elf level knowledge is probably inadequate. The answer obviously lies in between the two extremes given.

Training, checklists, and manuals should provide you with enough knowledge to operate your aircraft under most expected circumstances ... but not all. Some pilots will die because of edge cases that coincide with gaps in their knowledge. Others will damage their aircraft or incur excessive costs. The more complex the system, the greater the odds of that happening. If you want to reduce the odds of that happening to you, you will consistently take opportunities over a lifetime of piloting to broaden and deepen your knowledge of systems. Likewise for piloting skill, weather knowledge, etc.

IMO a really good way to do that is to participate in maintenance. It is one thing to read about a system or look at a diagram. It is another to get hands on, to take things apart and put them together.

A simple example would be engine controls. How many pilots understand the routing and attachment points of cables and sheaths for mixture, prop, throttle, carb heat/alt air, cowl flaps, etc? For new PPL that is probably close to zero, because most students flying rentals are taught the cowl is a forbidden zone, to be viewed only by peeping through the oil filler door. But if a control is not behaving the way you expect it to, having traced the cables and knowing where and how they are attached and secured might help you understand what the problem is, and what your options are.
 
Going back to the OP's question on constant speed propellers.

You are in cruise flight and the rpm suddenly increases and no longer responds to the propeller control. Why? What can you as the pilot do? What could happen if you do nothing?
 
midwestpa24 said:
Going back to the OP's question on constant speed propellers.

You are in cruise flight and the rpm suddenly increases and no longer responds to the propeller control. Why? What can you as the pilot do? What could happen if you do nothing?
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Immediate actions
  • Reduce throttle: Close the throttle to the idle position to reduce engine power and slow the propeller.
  • Pitch up: Gently raise the aircraft's nose to increase the angle of attack. This reduces the indicated airspeed and the load on the propeller, which can help decrease RPM.
  • Check oil pressure: This is a critical step, as many overspeed events are caused by oil system failure.
  • Follow the checklist: Refer to your aircraft's specific emergency checklist for the correct sequence of actions.
  • Use speedbrakes (if applicable): On larger aircraft, deploying speedbrakes can help slow the aircraft down more quickly.

Pretty much common sense. My first point is ss a pilot say renting a plane you go by check list pretty much. You really have no knowledge of said aircraft.

Owner aircraft you should know how many hours is on the prop and governor. When were they last overhauled. Does either one leak oil. Especially when were they removed for OH and a big one how many years ago was it done. 5 years ago? 25 years ago?

Rental planes you never know.
 
Salty said:
It's impossible to have all knowledge, but in every case ever -> More is better than less.
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You have not met my co-workers. The more knowledge they accrue, the worse their production quality becomes.
 
bonefishpete said:
Immediate actions
  • Reduce throttle: Close the throttle to the idle position to reduce engine power and slow the propeller.
  • Pitch up: Gently raise the aircraft's nose to increase the angle of attack. This reduces the indicated airspeed and the load on the propeller, which can help decrease RPM.
  • Check oil pressure: This is a critical step, as many overspeed events are caused by oil system failure.
  • Follow the checklist: Refer to your aircraft's specific emergency checklist for the correct sequence of actions.
  • Use speedbrakes (if applicable): On larger aircraft, deploying speedbrakes can help slow the aircraft down more quickly.

My first point is ss a pilot say renting a plane you go by check list pretty much. You really have no knowledge of said aircraft.
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I disagree. Knowing that an uncontrolled increase in RPM on most single engine airplanes is the failure mode when oil pressure is lost gives the pilot the ability to recognize the issues and do the first three bullet points. Knowing that the opposite will happen on most multi engine airplanes gives the pilot the ability to recognize and deal with the issues in those.
 
I think you need enough systems knowledge to be able to assess certain in-flight situations to properly troubleshoot and initiate an appropriate safety response. Some pilots are totally paralyzed when something unusual happens because they don't know how the airplane works, or what conditions constitute an emergency and which do not. Crashing a perfectly functioning airplane when a door pops open, battery fails, or a gyro goes tango uniform are classic examples.
 
Obviously, you need to know the systems. There's a legitimate question as to what degree is required to safely operate an airplane. For example, engines require air, fuel and spark to operate. If your engine stops operating or is running poorly, one of those is to blame. Out of fuel, carb ice, bad mag etc. I really don't need to know about flame fronts or valve timing to understand and diagnose these basic issues. There's obviously a bit more than that, but if your engine starts acting funky - Fuel, Air, Spark is good quick mental checklist. If your engine eats a valve in flight, knowing what that is ain't going to help the situation.

The fact that most airplane engines are 4 cycle and have an intake, compression, power and exhaust stroke isn't going to make a lot of difference in your ability to diagnose an issue. Yet that's one of the things taught and tested on.

Knowing more vs less is always better, but there's a good discussion about where that line is drawn.
 
RyanB said:
Is there any good reason for a pilot not to understand the systems they’re operating?
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That response doesn't explain why you thought the question was a joke. To answer your question, a pilot should understand the systems they are operating. Like so many things, an inexperienced person wouldn't know that because of of how other things work. A new pilot may expect that, like a modern car, there is little they can do once the engine stop except get out of the traffic if possible. Good flight instructors get their students out of that mind-set, but there are some that do not. Also, not knowing the OP, the question might also be "why do I need to know all this stuff?" because their instructor may be teaching it without explaining the "whys".

->Jack
What is obvious to one person rates a question from another
 
Hang 4 said:
Obviously, you need to know the systems. There's a legitimate question as to what degree is required to safely operate an airplane. For example, engines require air, fuel and spark to operate. If your engine stops operating or is running poorly, one of those is to blame. Out of fuel, carb ice, bad mag etc. I really don't need to know about flame fronts or valve timing to understand and diagnose these basic issues. There's obviously a bit more than that, but if your engine starts acting funky - Fuel, Air, Spark is good quick mental checklist. If your engine eats a valve in flight, knowing what that is ain't going to help the situation.

The fact that most airplane engines are 4 cycle and have an intake, compression, power and exhaust stroke isn't going to make a lot of difference in your ability to diagnose an issue. Yet that's one of the things taught and tested on.

Knowing more vs less is always better, but there's a good discussion about where that line is drawn.
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But do you know how to recognize a stuck valve? Can you differentiate between a stuck valve, a fouled plug, or carb ice? How severe of a problem is it? Is it a land now, land ASAP, or continue on kind of problem?

That is where knowledge is power.
 
Read the King Air story being analyzed right now in a parallel thread.

If the pilot had read and understood the POH, most likely they would have not died.

The entire POH of a new to you is a must read before the first flight Sometimes, a familiar type, but different year, the POH is mostly unchanged, but that variation was unique.
 
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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How would you explain how the blue knob controls the elf to a Cirrus pilot?
 
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Thanks for the thoughtful replies. Most of them seem to reference what I would describe as operation-level knowledge, and I am in complete agreement that we all need to understand our aircraft’s systems at that level. But is it important to drill down deeper, to really know and understand the machine at the nuts-and-bolts level?

I’m an unapologetic gearhead. I have swung wrenches on vehicles (occasionally with success, always with colorful language) since I was 15. While I stupidly never got an A&P, I spent a couple of years assisting an IA in a small shop: “Roger, this here is a Mooney. And this is a #2 Phillips screwdriver. And see these oval plates on the bottom of the wings with all of them rusty screws? …” It was fun and educational, and since then I have done nearly all of the gruntwork on my own planes under the highly diligent supervision of a good IA. Just so ya know where I’m coming from.

Many good points were made. In the interest of brevity (yeah, I know: too late for that) I would like to reply to a select few.
Tools said:
Me, I can’t read a digital watch without understanding how an escape mechanism works…. (Footnote)

*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.
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This is a good analogy that addresses the concept. An understanding of clockworks is nut-&-bolt-level knowledge that is meaningless to someone who just wants to know what time it is. Understanding that it’s a mechanical movement with a mainspring that has to be manually wound on a regular basis… well, that’s operation-level knowledge that would be quite essential, if one wishes to know the time.
farmrjohn said:
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.
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My first major airline had once operated Electras. Very similar engines & props to the Herc. One of the crusty graybeards I flew with was aghast that my training class was only six and a half weeks. He blustered, “my class all went to the Electra. We spent an entire week just on the [expletive deleted] propeller.” I wonder if he ever found a use for all of that information.
RyanB said:
I hope this is a joke.
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No, I’m dead serious! Little blue magic elves run the show. The whole thing about flyweights etc. is a grand conspiracy!
midwestpa24 said:
A perfect example of a lack of knowledge becoming a tragedy, the 737 Max MCAS system.
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Well, those pilots apparently didn’t know that MCAS even existed. Ultimate systems-knowledge failure. But an in-depth nuts-&-bolts understanding would not have been more useful to them, in the heat of the battle, than solid operation-level knowledge.
midwestpa24 said:
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?"
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But that’s not really it, at least, not all of it. More later. Maybe.
Dan Thomas said:
Carb ice is one of those things that can't be induced at will to demonstrate it. So the student needs to know what it's all about and the conditions conducive to it, what to do and what to expect. Anything less and he's severely handicapped.
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Agree with that, Dan. And all that is needed is a very basic understanding of how a carburetor (and the heat system) works. Operation-level stuff. I have been flying my plane for years without knowing a lot about the carburetor. Recently I studied an exploded diagram of the thing and the complexity was almost frightening. Lots worse than even an old Quadrajet. I wish I’d never seen it.
Ed Haywood said:
The question posed makes the standard internet error of forcing a false binary choice. No, you probably don't need advanced engineering knowledge in most cases. Yes, magic-elf level knowledge is probably inadequate. The answer obviously lies in between the two extremes given.
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Option two was intended as a rhetorical device, not a choice. Yes, somewhere in between. But where?
midwestpa24 said:
You are in cruise flight and the rpm suddenly increases and no longer responds to the propeller control. Why? What can you as the pilot do? What could happen if you do nothing?
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And you confirm that the oil pressure and temperature are normal. What could be the problem?
geezer said:
Read the King Air story being analyzed right now in a parallel thread.

If the pilot had read and understood the POH, most likely they would have not died.
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Jeez, the wreckage hasn’t even stopped smoldering yet. Call me old-fashioned, but I’ll wait for the NTSB findings.
 
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Roger Wilco said:
This is a good analogy that addresses the concept. An understanding of clockworks is nut-&-bolt-level knowledge that is meaningless to someone who just wants to know what time it is. Understanding that it’s a mechanical movement with a mainspring that has to be manually wound on a regular basis… well, that’s operation-level knowledge that would be quite essential, if one wishes to know the time.
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This one resonates with me…D23E3F4B-EAEC-4F28-B5CA-6F2A4405F5D5.jpeg

Repairing and regulating vintage mechanical watches is a hobby I started a few years ago (and I daily wear a 1954 Elgin wristwatch, it’s not chronometer accurate yet, but pretty darn close). The “nuts and bolts” of them seems simple, the magic harmony of all the pieces working in rhythm to precisely do exactly what they are supposed to do is much more complicated than it looks . (This pocket watch movement had a single eyelash in it that found its way into the lower escapement bearing jewel and wound up make it stop when it was turned over. It had probably been inside it since it was made in 1912 and eventually found its way into that spot.

I think it a matter of expectations. Can you operate the aircraft knowing only the controls and letting the magic ferries take care of the rest 99.99999% of the time? Probably yes, if that is what your happy with. Do you want to become a master of your machine, somebody who can make a decision at a critical moment that may latter be referenced in training material for years to come… that doesn’t come by luck, it comes from knowing every single system and component.
 
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MauleSkinner said:
I disagree. Knowing that an uncontrolled increase in RPM on most single engine airplanes is the failure mode when oil pressure is lost gives the pilot the ability to recognize the issues and do the first three bullet points. Knowing that the opposite will happen on most multi engine airplanes gives the pilot the ability to recognize and deal with the issues in those.
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What part did you disagree with? Just wondering.
 
midlifeflyer said:
You can if you want to.
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It’s hard too unless they let you remove the cowling, interior panels. You can ask for log books buy they don’t have to let you.

Best part of owning a plane and doing oil and plugs is it gets you inside look at everything.

How many rental planes do you pull the seats and have a really good look under the panel?

Hope you understand what I’m getting at that you rely on the maintenance that was done with no input.

When I rented planes I gave them a really good pre flight and left it at that.
 
bonefishpete said:
Best part of owning a plane and doing oil and plugs is it gets you inside look at everything.
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One of the reasons I still do my own oil changes and tire rotation on the cars, I get to get under there and put an eyeball on everything. Brake pads and rotors, check the rubber brake hoses, check struts/shocks for leaks, check CV joint boots, check other various suspension joint boots, look for signs of other leaks, etc.
 
Roger Wilco said:
My first major airline had once operated Electras. Very similar engines & props to the Herc. One of the crusty graybeards I flew with was aghast that my training class was only six and a half weeks. He blustered, “my class all went to the Electra. We spent an entire week just on the [expletive deleted] propeller.” I wonder if he ever found a use for all of that information.
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I spent two weeks on Electra training. That propeller system does indeed justify days of training. The governor is a huge thing that mounts to the backside of the prop and rotates with it. It has four hydraulic valves on its periphery that sense various factors and feed into the adjustment of the blades. There are electrical systems in it, too, controlled by slip rings and brushes carrying signals from the pilots. It's the green thing, here:

1763138803372.jpeg

The propeller itself spans over eleven feet, weighs over 1000 pounds and in flight, rotates at about 1050 RPM.

Re the prop speed runaway:
Roger Wilco said:
And you confirm that the oil pressure and temperature are normal. What could be the problem?
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If the governor control cable disconnects from the governor control arm, a spring sends the governor setting to full RPM.
 
bonefishpete said:
You can ask for log books buy they don’t have to let you.
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I have been a renter/club member for all of the 35 years I have been flying. I've rented in Massachusetts, Connecticut, Florida, California, North Carolina, South Carolina, New York and probably a few I've forgotten. So far, I have not come across one which would deny a customer the ability to view the aircraft logbooks if they wanted to check something. I figure it would take one checkride discontinuance when the DPE asked the applicant to prove airworthiness and all they had was a dispatch sheet (let alone an investigation into a pilot for flying something unairworthy).

That sort of happened with my first private pilot student. Dispatch sheet showed the airplane was current, but it had been out of annual for several months. My student - of course - checked the logbooks that morning and discovered what everyone else had missed or not looked for.
 
Dan Thomas said:
I spent two weeks on Electra training. That propeller system does indeed justify days of training.
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No doubt, it’s a marvel of complexity. But if I’m correct, your training was aimed at AMTs who have to diagnose, repair, and overhaul the beast. From a pilot perspective, far less knowledge would be required in order to operate it.
 
A good example of a pilot who did not understand his systems, and died for it:

Hengelo

Thread 'Plane down Little Rock'

bnonews.com

Small plane crash at Little Rock Airport, 1 killed

A small plane has crashed while trying to take off from Little Rock International Airport in Arkansas, local officials say. The pilot – who was the only person on board – was killed. The accident happened at 1:16 p.m. on Sunday when the aircraft, a Cirrus SR22, was rolling down one of the...
bnonews.com bnonews.com
  • Sad
 
midwestpa24 said:
A perfect example of a lack of knowledge becoming a tragedy, the 737 Max MCAS system.
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Not really, pitch runaway is something covered in training... but you gotta understand what the airplane is telling you in order to correct it.

Also MX was a contributing factor so even after QRH the crashed planes would still not respond properly.

So not really a perfect example.
 
When I first started flying jets, I was expected to know that the secondary fuel nozzles were positioned at the 2 and 8 o’clock stations in the second stage burner.

Later in my career the FAA realized that nothing can be done about a fuel nozzle from the cockpit.
 
I think if you can draw a sketch of the system from memory that would suffice if it were detailed enough to explain how it works yet not detailed enough to build it.
 
Brad Smith said:
Ernest K. Gann tells a story of an experience in “Fate is the Hunter” that he had while flying a DC-4. The intakes on the cowlings were icing over and the engines were being starved of air. The pilot knew enough about his engines to intentionally backfire the engines throgh the carbs to blow out the buildup of ice in the intakes. If it wasnt for that, that plane would’ve gone down for sure. Knowledge on engine operation above and beyond what the POH needed was what saved the day.
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Try SCE to Aux.

RyanB said:
Is there any good reason for a pilot not to understand the systems they’re operating?
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But to what level? At a certain point, more knowledge isn't going to help, and knowledge of anything you can't affect from the cockpit in flight is likely useless.
 
There are many examples where a general knowledge of systems can be extremely useful in preventing someone from making bad choices. Here are few I have come across:

Fuel selector valve - We once had a pilot decide that placing the valve halfway between Both and Right would draw “slightly more” fuel from the right tank. Instead, the engine quit - fortunately at a high enough altitude for a successful glide to a nearby airport. A basic understanding of how ball valves work would have revealed that “halfway” does not provide half of each.

Leaning - In carbureted engines, do we lean for density altitude or for power? There is constant confusion over this. POH is of no help, since most of them just tell you to adjust mixture as needed. In reality, we lean for both altitude and power, because any change in either alters the fuel–air ratio. The mathematics of why this is the case is very insightful. It means, we have to lean for taxi power (to avoid plug fouling, if that is an issue), and then set mixture again for takeoff power, even though we are at the same elevation.

There's more, though I can't think of them all right now.

Then there are anecdotal information passed down that are either inaccurate or incomplete which a more logical and curiosity-driven mindset could unravel.
Oversquare operation - in most airplanes, there is no such thing.
Shock cooling - ok, this may still be up in the air, but I maintain that in the ordinary NA pistons that we fly, it's not possible to shock cool under normal operations. Air simply does not have the thermal conductivity or thermal capacity to quench a hot metal at a rapid rate. If it did, welders could use a fan instead of a bucket of water.

I've heard some pilots, and instructors too, maintain the view that we should just focus on flying and leave the mechanical details to the mechanics. I couldn't disagree with that more. The more we ask the questions "what if" and "why" the better and safer pilots we become.
 
StraightnLevel said:
Judgement exercised without thorough comprehension of the underlying systems involved in the situation is no more valuable than superstition.
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After giving this some thought, it seems that we have to define “thorough comprehension,” for the purpose of flying the airplane. For any combination of pilot and aircraft, there are undoubtedly one or more systems/components for which a true expert could identify significant gaps in the pilot’s knowledge. Using Kritchlow’s example in #74, would you characterize his knowledge of the location of the secondary fuel nozzles as “thorough comprehension?” If so, I would reply by agreeing with Kritchlow’s point that such knowledge was superfluous and entirely useless from a pilot’s perspective, and go on to add that even that level of comprehension would be far from thorough.
StraightnLevel said:
Checklist = religion
Systems understanding = science
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I like the way that this reads. But I don’t grasp what you mean when you equate checklists to religion. Would you elaborate?
 
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