Pilot Zhuang Qu learns the importance of that big watch he's wearing

[mandm]

You are correct that if you pull the mixture all the way back you’ll starve the engine of fuel, and it will stop producing power. However the airflow through the prop will still keep the prop turning just like wind turns a windmill. In order to have the prop stop turning, you need to either feather the blades to align them with the direction of flight (not something that you can usually do on piston singles) or reduce the airflow through the prop disk enough that the compression of the engine stops the prop.

The prop doesn’t just stop spinning when the engine stops (as long as there’s sufficient airflow)

I never really thought about it. So let’s say the engine stopped in flight because the mixture was leaned, if mixture rich would that send fuel and the windmilling prop would push the engine through the cycles thereby starting automatically without even using the ignition switch? Or ignition switch is required to create spark?

 

[jimhorner]

I never really thought about it. So let’s say the engine stopped in flight because the mixture was leaned, if mixture rich would that send fuel and the windmilling prop would push the engine through the cycles thereby starting automatically without even using the ignition switch? Or ignition switch is required to create spark?

The spark is created by the magnetos. Assuming you haven’t switched them off in flight, they’ll still be providing a spark as long as the crankshaft is turning. Give the engine a proper fuel air mixture again, and it will most likely restert.

If you pulled the mixture back to idle in flight, pushng it forward again would likely do the trick, but, if you’re flying a low wing, you might need to give it a shot of the fuel boost pump.

I’m guessing you’re a student pilot? What type of aircraft are you learning in? Fuel injected or carburated? It would probably be a good idea to sit down with your instructor to get a good understanding of these systems.

It can all be a bit confusing at first. I started learning at age 12 from my father. We started the plane (cessna 172D) by priming, switching on the master and then turning the key. However, we stopped the engine by pulling the mixture? And _then_ turned off the master and the key? And the master could be turned off after the engine started with no effect on the engine, yet it had to be on to start the engine? And either turning the key or pulling the mixture stopped the engine, but the way to do it was to pull the mixture? It was very confusing to me until my father, engineer that he was, drew it all out for me with schematics and diagrams.

Not much like a car where one uses a key and only the key to start and stop the engine. It will all be much clearer once you really understand the purpose of the master switch, the mixture, the throttle, the magnetos, and the ignition/starter key.

 

[GeorgeC]

Or ignition switch is required to create spark?

The ignition (mags) needs to be on. It's the starter you don't need. Some planes have mag switches and a separate pushbutton for the starter.

 

[mandm]

The spark is created by the magnetos. Assuming you haven’t switched them off in flight, they’ll still be providing a spark as long as the crankshaft is turning. Give the engine a proper fuel air mixture again, and it will most likely restert.

If you pulled the mixture back to idle in flight, pushng it forward again would likely do the trick, but, if you’re flying a low wing, you might need to give it a shot of the fuel boost pump.

I’m guessing you’re a student pilot? What type of aircraft are you learning in? Fuel injected or carburated? It would probably be a good idea to sit down with your instructor to get a good understanding of these systems.

It can all be a bit confusing at first. I started learning at age 12 from my father. We started the plane (cessna 172D) by priming, switching on the master and then turning the key. However, we stopped the engine by pulling the mixture? And _then_ turned off the master and the key? And the master could be turned off after the engine started with no effect on the engine, yet it had to be on to start the engine? And either turning the key or pulling the mixture stopped the engine, but the way to do it was to pull the mixture? It was very confusing to me until my father, engineer that he was, drew it all out for me with schematics and diagrams.

Not much like a car where one uses a key and only the key to start and stop the engine. It will all be much clearer once you really understand the purpose of the master switch, the mixture, the throttle, the magnetos, and the ignition/starter key.

I started flying this year, albeit did a discovery flight some odd 10+ years ago. I have my PPL and am scheduling the checkride for my Instrument rating. I fly in Cessna 172p (carb heat), Cessna 172s (fuel injected), DA40 (only once), Arrow (fuel injected) and Mooney (only once, fuel injected).

Normal process for turning off is trim for takeoff, flaps up, transponder 1200, avionics off, lights off, mixture lean, turn off master & mags(key).

Normal process for turning on varies and usually the instructor guides the process.

Carb heat —> mixture rich + start
Carb heat (cold start) —> primer pump, lock primer, rich + start
Fuel injected —> mixture lean, start and push mixture to rich as it catches
Fuel injected (cold start) —> fuel pump on, mixture rich plus throttle to see fuel flow for 2-3 seconds, fuel pump off, mixture lean, start and push mixture to rich when catches.

 

[mandm]

I would say I don’t fully understand it but I got the gist of it. Over time I try to learn something in more detail step by step. But I don’t think it’s fully explained. I still don’t understand the constant prop (yes I understand the angle of the proper adjusts with the blue handle), but I don’t understand the mechanics of how that’s possible. Was told it’s by the oil but I cannot get my mind on it. One day.

My university degree is also in Mechanical Engineering.

 

[jimhorner]

I would say I don’t fully understand it but I got the gist of it. Over time I try to learn something in more detail step by step. But I don’t think it’s fully explained. I still don’t understand the constant prop (yes I understand the angle of the proper adjusts with the blue handle), but I don’t understand the mechanics of how that’s possible. Was told it’s by the oil but I cannot get my mind on it. One day.

My university degree is also in Mechanical Engineering.

Just remember, PPL is a license to learn. For me, that included learning more about aircraft systems. A significant part of my preparation for the Commercial certificate was learning the details of those systems. Commercial pilots are expected to have a pretty good understanding of the systems. Good practice for Private pilots as well.

Constant speed props 101: https://www.boldmethod.com/learn-to-fly/aircraft-systems/how-a-constant-speed-prop-works/

 

[mandm]

Just remember, PPL is a license to learn. For me, that included learning more about aircraft systems. A significant part of my preparation for the Commercial certificate was learning the details of those systems. Commercial pilots are expected to have a pretty good understanding of the systems. Good practice for Private pilots as well.

Constant speed props 101: https://www.boldmethod.com/learn-to-fly/aircraft-systems/how-a-constant-speed-prop-works/

Thanks for sharing the article. I was watching a YouTube video previously and gave up. At least this shows where the oil goes and how it’s controlled. Makes a bit more sense now!

I am always learning, still taking lessons, studying for my commercial as well. Hope to do some right seat training too.

 

[Rgbeard]

I’m new to aviation, never tried to stop and restart the engine. Setting the throttle to idle is what I have done. I just thought if you leaned the mixture that it would turn the engine off? I don’t understand all the mechanics yet either.

If you lean back the mixture, no fuel is mixed with the incoming air. Thus: no bang.

but the mighty wind in front of you against those blades keeps the machine spinning.

it doesn’t “turn off” anything.

 

[Rgbeard]

My university degree is also in Mechanical Engineering.

you have a university degree in mechanical engineering and a Fred-Flintstonesqe oil-operated RPM governor has you stumped?

I’m sad.

 

[Rgbeard]

Your flight instructor has some serious skin in the game here. Just sayin’.

 

[mandm]

you have a university degree in mechanical engineering and a Fred-Flintstonesqe oil-operated RPM governor has you stumped?

I’m sad.

Never worked in the industry
Also didn’t look into it that much

 

[Rgbeard]

Never worked in the industry
Also didn’t look into it that much

wow.

for the WIN!

 

[Clip4]

Somebody at Piper wrote this in a POH.

Always remember that the electric fuel pump should be turned “ON” before switching tanks, and should be left on for a short period thereafter. In order to keep the airplane in best lateral trim during cruising flight, the fuel should be used alternately from each tank. It is recommended that one tank be used for one hour after takeoff, then the other tank be used for two hours: then return to the first tank, which will have approximately one and one half hours of fuel remaining if the tanks were full at takeoff. The second tank will contain approximately one half hour of fuel. Do not run tanks completely dry in flight. The electric fuel pump should be normally “OFF” so that any malfunction of the engine driven fuel pump is immediately apparent. If the signs of fuel starvation should occur at any time during flight, fuel exhaustion should be suspected, at which time the fuel selector should be immediately positioned to the other tank and the electric fuel pump switched to the “ON” position.

 

[Lindberg]

It greatly improves your chance at living though.

Yes, but not as much as restoring fuel flow to the engine does.

 

[PaulS]

Yes, but not as much as restoring fuel flow to the engine does.

Well, depends, stall/spin greatly increases your chance of death.

That said, if I immediately understood my mistake then I would probably switch the tank quickly if not first thing and turn on the fuel boost. But this guy was clueless as I would probably be for an issue not induced by stupidity ( I watch fuel closely, plus there are other clues when it starts getting close in most airplanes. So if I'm clueless as to the reason for the engine shutting down, I'd go to my flow, which would set best glide and get pointed to an airport or field first up.

 

[PaulS]

Somebody at Piper wrote this in a POH.

Always remember that the electric fuel pump should be turned “ON” before switching tanks, and should be left on for a short period thereafter. In order to keep the airplane in best lateral trim during cruising flight, the fuel should be used alternately from each tank. It is recommended that one tank be used for one hour after takeoff, then the other tank be used for two hours: then return to the first tank, which will have approximately one and one half hours of fuel remaining if the tanks were full at takeoff. The second tank will contain approximately one half hour of fuel. Do not run tanks completely dry in flight. The electric fuel pump should be normally “OFF” so that any malfunction of the engine driven fuel pump is immediately apparent. If the signs of fuel starvation should occur at any time during flight, fuel exhaustion should be suspected, at which time the fuel selector should be immediately positioned to the other tank and the electric fuel pump switched to the “ON” position.

Yes, Cirrus does it in this order too, switch tank and then boost, opposite of what a normal tank switch is. I was told that the POH is like this so that if the starvation is caused by crud in the tank you won't suck an extra amount in due to the aux fuel pump. Made sense to me.

 

[woodchucker]

In the Tiger I usually just switch tanks without the electric boost pump. Never a hiccup. I also switch every 30 minutes. I guess the difference is around 25 pounds vs 50 pounds differential if done every hour.

I feel bad for this pilot, or any pilot, that crashes due to self-inflicted fuel starvation.

 

[Lindberg]

Well, depends, stall/spin greatly increases your chance of death.

If you stall/spin/crash because you're unable to control airspeed and avoid a stall while switching tanks, you have big problems.

 

[PaulS]

If you stall/spin/crash because you're unable to control airspeed and avoid a stall while switching tanks, you have big problems.

If you leave your fuel set to one tank, run it dry then crash with the other tank full you have big problems. Airspeed is king and should be the first consideration. We are assuming cruise flight here, but engines go TU on the initial climb out where if you get distracted trying switch a fuel tank before you establish a glide, you can easily kill yourself.

 

[Bill]

If you leave your fuel set to one tank, run it dry then crash with the other tank full you have big problems. Airspeed is king and should be the first consideration. We are assuming cruise flight here, but engines go TU on the initial climb out where if you get distracted trying switch a fuel tank before you establish a glide, you can easily kill yourself.

Yup. I should try it some time at altitude, but I'd figure if the mill dies on a Vx climb, you're going to need an aggressive push over to keep flying.

 

[MauleSkinner]

Yup. I should try it some time at altitude, but I'd figure if the mill dies on a Vx climb, you're going to need an aggressive push over to keep flying.

Depends upon your definition of “aggressive”, but yes. And if you’re climbing at Vx, the pull to arrest the sink rate to land will probably be just as aggressive. And there will be somewhere between 3 and 7 eternities in between the push and the pull, during which there will be entirely too much dirt in the windshield.

 

[denverpilot]

We need to not guess and wait for official NTSB news! LOL...

Oh man that still makes me laugh. Interns...

 

[Clip4]

While you folks are getting a chuckle, fuel mismanagement is a risk with students in low wing trainers and the the CFI probably did not consider fuel mismanagement risk in the student restrictions. The CFI risk management solution is full fuel prior to each flight. Local solo limited to 1.5 hours. Refuel each airport on an XC with no leg longer than 1.5 hours. Even if they don’t switch tanks, they shouldn’t run dry.

 

[3393RP]

While you folks are getting a chuckle, fuel mismanagement is a risk with students in low wing trainers and the the CFI probably did not consider fuel mismanagement risk in the student restrictions. The CFI risk management solution is full fuel prior to each flight. Local solo limited to 1.5 hours. Refuel each airport on an XC with no leg longer than 1.5 hours. Even if they don’t switch tanks, they shouldn’t run dry.

I'm getting a bigger chuckle out of the supposition that routine contingencies must be made to ameliorate student fuel mismanagement after they are released for solo flight. At what point do they get released without enough fuel to go from point A to B unless there is some sort of pilot intervention? What other basic flight tasks are they deemed incapable of performing? When are they just cut loose? A hundred hours? Two hundred?

 

[Clip4]

I'm getting a bigger chuckle out of the supposition that routine contingencies must be made to ameliorate student fuel mismanagement after they are released for solo flight. At what point do they get released without enough fuel to go from point A to B unless there is some sort of pilot intervention? What other basic flight tasks are they deemed incapable of performing? When are they just cut loose? A hundred hours? Two hundred?

Under my signature you don’t and you are going to be subject to a number of other restrictions.

When you see as many Low wings taxi into the pumps with 1 tank full and the other less than 1/4 full you figure this stuff out.

 

[MauleSkinner]

Under my signature you don’t and you are going to be subject to a number of other restrictions.

When you see as many Low wings taxi into the pumps with 1 tank full and the other less than 1/4 full you figure this stuff out.

How many times do they have to get it right before you endorse them for a checkride?

 

[Clip4]

How many times do they have to get it right before you endorse them for a checkride?

During the planning review for the XC planning they have to have specific points on their planning for tank switch. None of that has any thing to do with the check ride.

 

[MauleSkinner]

During the planning review for the XC planning they have to have specific points on their planning for tank switch. None of that has any thing to do with the check ride.

So “Operate at least three of the systems listed in K1a through K1l above appropriately.” doesn’t include the fuel system?

 

[Clip4]

So “Operate at least three of the systems listed in K1a through K1l above appropriately.” doesn’t include the fuel system?

We are talking about humans. We can train them, the question is their actions during solo. As a CFI you can minimize risk or ignore it and leave it to human behaviour. As long as its on your signature it makes me no difference.

 

[MauleSkinner]

We are talking about humans. We can train them, the question is their actions during solo. As a CFI you can minimize risk or ignore it and leave it to human behaviour. As long as its on your signature it makes me no difference.

Your signature on a recommendation says they meet standard and are ready to test. If your student came back from every solo XC with 1/4 tank in on one side and full in the other, despite planning that said he was going to switch tanks, he didn’t operate the fuel system appropriately, and you’d be signing someone off for a checkride who never demonstrated the standards to which you’re supposed to be training. That’s not minimizing risk, it’s encouraging the occurrence that resulted in this thread.

 

[Clip4]

Your signature on a recommendation says they meet standard and are ready to test. If your student came back from every solo XC with 1/4 tank in on one side and full in the other, despite planning that said he was going to switch tanks, he didn’t operate the fuel system appropriately, and you’d be signing someone off for a checkride who never demonstrated the standards to which you’re supposed to be training. That’s not minimizing risk, it’s encouraging the occurrence that resulted in this thread.

I not talking about my student. My students stopped, refueled self serve, calculated their fuel use and discovered their own mistake.

 

[MauleSkinner]

I not talking about my student. My students stopped, refueled self serve, calculated their fuel use and discovered their own mistake.

Mr. Qu apparently discovered his own mistake as well.

 

[Clip4]

Mr. Qu apparently discovered his own mistake as well.

Yes he did, the key is to break the chain of events

 

[MauleSkinner]

Yes he did, the key is to break the chain of events

Yup...and demonstrating that you consistently can’t break the chain of events until after the events are complete does not meet standard for a checkride signoff.

but like you said, what you do with your signature is your business.

 

[bbchien]

I have had a student violate my well designed cross country solo, by (1) not refueling at MSN and (2) not securing the primer all the way in on the return trip (whcih I found upno inspection). He had 2 gals on the tank he was flying on, when he rolled out, consistent with the added flow of ~ 2gph from fuel bypass. He got an earful upon his return.

He was "running behind" and chose to not refuel at the farpoint, "calculating that I had more than enough fuel". And he switched tanks back to the near empty tank upon MSN departure.

A student solo is stressful. CFIs need to understand that even with their best prep, he's gonna be a lizard out dere. That that is why the CFI has to personally approve the plan and he better take due care.

CALCULATIONS go awry.

 

[PPC1052]

How much time would it take to restart the engine. So fuel pump on, switch tanks, mixture rich throttle in some fuel, fuel pump off, mixture where needed, start?

What if it never re-starts?

 

[jimhorner]

What if it never re-starts?

Than you're flying a glider, and it's a good idea to have a landing spot picked out.


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[PPC1052]

Than you're flying a glider, and it's a good idea to have a landing spot picked out.


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Well, that's my point. Pitch for best glide first to give more options.

 

[jimhorner]

Well, that's my point. Pitch for best glide first to give more options.

I would agree when the engine stopage is unforeseen. If my engine stops, and it's a surprise, then yes, absolutely pitch for best glide and then diagnose and try to correct the issue. However, as I indicated earlier in the thread, intentionally running a tank dry is a valid strategy for getting maximum range. When I run a tank dry, I'm expecting it, and my first actions are to switch tanks and give the electric boost pump a shot, not to pitch to best glide. Takes a few seconds and the engine is back to life and running fine.


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[PPC1052]

I would agree when the engine stopage is unforeseen. If my engine stops, and it's a surprise, then yes, absolutely pitch for best glide and then diagnose and try to correct the issue. However, as I indicated earlier in the thread, intentionally running a tank dry is a valid strategy for getting maximum range. When I run a tank dry, I'm expecting it, and my first actions are to switch tanks and give the electric boost pump a shot, not to pitch to best glide. Takes a few seconds and the engine is back to life and running fine.


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Makes sense. But that's a different situation than to which my first post was a response.