Carb heat broken, ok to fly?

[fugazi885]

Hi, I am a student pilot with very low time. Today was my third flight and during the runup the carb heat knob pulled out much farther than normal and there was no drop in engine RPM indicating the linkage had broken or become disconnected. My instructor seemed OK to still fly the plane as it was a very hot day and we shouldn't really need it. I figured if it is on the checklist and fails, don't fly. We taxied back and did not fly because I didn't trust it, did I make the right call? Also, should I be billed for the hobbs time we were in the plane for something like this?

 

[Tantalum]

did I make the right call?

Yes. My interpretation of the regulations is that if there is broken equipment on the airplane you are not technically allowed to fly it unless XYZ occur (not required for the type of flight, ie day VFR, IFR, etc) and that it has been properly "inop'd" , etc.

should I be billed for the hobbs time we were in the plane for something like this

That will depend on the club and local policies. Definitely worth asking. I've heard arguments from both sides, from owners that you should still get charged because you were still logging time. And then from renters that it's not really fair to be charged for broken equipment

 

[AggieMike88]

One of the FARs you need to know is §91.205. Read paragraph (b) and tell us what that said about required items.

And while that is the rules, there is zero issues with being appropriately cautious and scrubbing the flight due to a maintenance issue. Better safe and alive than macho and hurt.

Edit: oops.. forgot §91.213... thanks @Tantalum!

 

[rk911]

yup, for all of the above reasons plus carb icing can occur in hot weather. i'd protest any charges resulting from the scrub. you were not PIC as this was just your third flght.

 

[Half Fast]

Keep in mind that this was an indication of something wrong with the carb, and you don't know what broke, nor why, nor that something else isn't about to go wrong with the carb. Even if you didn't encounter icing, there could be a loose fastener, a broken piece of cable, a detached spring, etc., that could cause a throttle problem at some inopportune moment.

IMHO, it's not enough to just decide something is not needed and mark it INOP. You must also ensure that the fault cannot cause a secondary failure. That's not from the FAR, that's from a paranoid pilot who is an engineer who has led numerous failure investigations for missile flights.

 

[RyanB]

If carb heat fails, it’s a no fly, especially if the linkage comes apart.

As for being billed, I wouldn’t be surprised if you are, but you shouldn’t be. Still would need to pay for the CFI’s time, but not the aircraft rental.

 

[Tantalum]

it's not enough to just decide something is not needed and mark it INOP

Agree. That part of the FAR is abused imho

 

[WannFly]

I won’t fly with carb heat not working, even though in an archer, I have never used it in 230 hrs in all sorts of condition. Carb ice can occur in hot days as well, there is a chart on AFH the that shows it.

For the CFI this was a good teaching moment that he missed IMO.

 

[SkyDog58]

Ok, a quick question for you. In what position did it fail? Two possibilities.

The carb heat was off and when you tried to turn it on, it failed so it remained off.

On the previous landing after carb heat was on and then the knob was pushed back in, did it break then, leaving it in the on position?

Do you know?

 

[Half Fast]

Still would need to pay for the CFI’s time, but not the aircraft rental.

Depends. If he's renting a plane and hiring his own instructor, I agree. But if he's paying a flight school that provides the plane and employs the instructor, he shouldn't have to pay anything and the school should cover the CFI's time.

 

[RyanB]

Depends. If he's renting a plane and hiring his own instructor, I agree. But if he's paying a flight school that provides the plane and employs the instructor, he shouldn't have to pay anything and the school should cover the CFI's time.

Good point.

 

[fugazi885]

Ok, a quick question for you. In what position did it fail? Two possibilities.

The carb heat was off and when you tried to turn it on, it failed so it remained off.

On the previous landing after carb heat was on and then the knob was pushed back in, did it break then, leaving it in the on position?

Do you know?

Good question, I believe it was broken on the previous flight. I pulled it out and did not feel anything break, it just pulled out a lot farther than normal and no change in RPM. So in this situation the carb heat could have actually been stuck on, not off like we presumed?

 

[SkyDog58]

Good question, I believe it was broken on the previous flight. I pulled it out and did not feel anything break, it just pulled out a lot farther than normal and no change in RPM. So in this situation the carb heat could have actually been stuck on, not off like we presumed?

Yes. It could have been.

 

[AKBill]

As for being billed, I wouldn’t be surprised if you are, but you shouldn’t be. Still would need to pay for the CFI’s time, but not the aircraft rental

Agreed

Depends. If he's renting a plane and hiring his own instructor, I agree. But if he's paying a flight school that provides the plane and employs the instructor, he shouldn't have to pay anything and the school should cover the CFI's time.

Good point

Good question, I believe it was broken on the previous flight. I pulled it out and did not feel anything break, it just pulled out a lot farther than normal and no change in RPM. So in this situation the carb heat could have actually been stuck on, not off like we presumed?

Carb heat normally fails in the off position. It's a cable connected to a flap below the carb that changes the intake air flow from filtered air to heated air from the exhaust.

 

[Marcelo Silva]

Hi, I am a student pilot with very low time. Today was my third flight and during the runup the carb heat knob pulled out much farther than normal and there was no drop in engine RPM indicating the linkage had broken or become disconnected. My instructor seemed OK to still fly the plane as it was a very hot day and we shouldn't really need it. I figured if it is on the checklist and fails, don't fly. We taxied back and did not fly because I didn't trust it, did I make the right call? Also, should I be billed for the hobbs time we were in the plane for something like this?

This happened to me while on the pattern at an untowered airport. I didn't know whether carb heat was on or off as the know came off in my hand.
My CFI elected for us to abort the landing and go back to home base, 20 nm away. We flew the plane at 2200 rpm as to not overstress the engine if carb heat was on but also into the green rpm range in case it was off. We landed then grounded the plane.

 

[kath]

Right call, fugazi885.

 

[pburger]

Good call!! Trust your instincts!!

When I was a student, I took a 150 out for some solo practice, and had a bad run-up. I tried leaning to clear the fouled plug(s), but it didn't clear up. I sat there in the run-up area wondering what to do. I realized that no one had specifically told me that if I have a bad run-up, to not go. Common sense dictated that I should not go, so I taxied back to the flight school. A couple of guys were laughing at me because I wasn't able to clear a fouled plug. Then one of the owners, who was also an A&P, opened the cowling and found a plug wire not connected! BAM! Apparently they had done some work prior to me taking the plane. I felt good about my instincts, and it shut up the idiots laughing at me.

 

[Stewartb]

I had a friend who flew with a known problem with his carb heat. The weather changed. He crashed into the sea when he failed to glide to the nearest land and drowned. The suspected cause was carb ice.

Don't fly without all the required tools!

 

[eetrojan]

Hi, I am a student pilot with very low time. Today was my third flight and during the runup the carb heat knob pulled out much farther than normal and there was no drop in engine RPM indicating the linkage had broken or become disconnected. My instructor seemed OK to still fly the plane as it was a very hot day and we shouldn't really need it. I figured if it is on the checklist and fails, don't fly. We taxied back and did not fly because I didn't trust it, did I make the right call? Also, should I be billed for the hobbs time we were in the plane for something like this?

Hi fugazi885 - The guys above have it right. 91.205(b) lists the equipment you need for daytime VFR, but more broadly, you need to dig through and understand 91.213(d) which, in just one small place, references 92.205(b). In other words, 91.213 is the spine of the whole thing and there are several other 91.213 factors in addition to the equipment specified in 91.205.

One of the factors you need to consider in order to decide whether or not it's legal to take off with inoperative equipment is 91.213(d)(2)(ii) which asks you to think about whether the equipment is in the aircraft's "required equipment list."

I don't know if your plane is a Cessna 172, but here are some relevant excerpts from the POH for the carbureted 172P that I fly sometimes. Carb heat is "-R" or "Required" equipment. So, as I understand it, the carb heat MUST be operative to make it legal for you to take off.

Joe

ps My school always no-charged me on the one or two occasions I discovered an airworthiness issue. When I quickly returned to the airport with a stuck elevator trim tab and 0.5 hrs on the Hobbs, I had to press it up above the dispatcher to the owner, but it was ultimately written off.

 

[wilkersk]

Also, should I be billed for the hobbs time we were in the plane for something like this?

The better question is, if the owner of the aircraft/flight instructor's employer condones the kind of behavior that makes you question whether or not you did the right thing, and doesn't take action to educate you why it was or was not the right thing, is that the place you want to continue to spend your flight instruction dollars?

 

[LoLPilot]

Hi, I am a student pilot with very low time. Today was my third flight and during the runup the carb heat knob pulled out much farther than normal and there was no drop in engine RPM indicating the linkage had broken or become disconnected. My instructor seemed OK to still fly the plane as it was a very hot day and we shouldn't really need it. I figured if it is on the checklist and fails, don't fly. We taxied back and did not fly because I didn't trust it, did I make the right call? Also, should I be billed for the hobbs time we were in the plane for something like this?

You absolutely made the right call. Even if it wasn't in the POH, you said it all in, "I didn't trust it." Don't fly something you don't trust. Both of my primary CFI's told me that. I scrubbed a solo CC because once I got the plane to cruise I kept losing RPM. It wasn't ice and I finally noticed that the throttle kept working its way out. I turned around and went back. One of our mechanics went out with me to the plane and found that the friction lock wasn't engaging properly. He fixed it for me, tested it real quick and said I was good to go. I didn't think I had enough daylight left to do the CC so I did a solo practice flight that ended up being one of the most memorable (for a good reason) flights of my PPL.

 

[asicer]

Nothing much to add except that carb heat is considered an alternate air intake in case the primary intake has a problem. You gotta consider whether or not you are OK with the decreased redundancy.

 

[brcase]

I have had a carb heat cable break during flight. I could tell because I immediately lost 400 RPM on Warm day where I would not have expected Carb Ice, but when I pulled the Carb Heat the cable pulled about 6 inches out when I concluded it had broken. After about a minute (a long time) the RPM came back up to about only a 200RPM drop while I diverted to the nearest airport for repairs, The carb heat was spring loaded to turn on in the event of a cable failure on an o-290.

Did you Log the time? If Yes then you should pay for it IMO. It was a training, maybe even better training than what you had planned.

Brian
CFIIG/ASEL

 

[brcase]

Once upon a time I might have just said if anybody asks, it worked when we did are run up and we will report it Maintenace after the flight.

One cold morning during start up the Master switch initially did not engage, cycling a couple times it engaged and we started the engine but the Low Voltage light did not go off after the start. Normally I would have aborted the flight right there, however thinking the Master switch was still having an issue due to the cold, I decided to proceed with the run up. A factor was I knew one of my students was doing the his oral for this Checkride and was scheduled to fly the plane after me with the DPE, I was hoping the issue was temporary due only the cold and warming the the airplane would resolve it. I proceed with the run up but were unable to get the alternator to come on line. I should have aborted the flight there or even sooner, but instead opted make a lap around the pattern hoping it would resolve itself, which it did not. I aborted the flight and advised the DPE and Maintenace that the airplane was grounded. When Maintenace started asking some questions about why I had flown the airplane, I initially started to mis-lead them saying that it failed in flight, but quickly realized that was the wrong thing to do and was a poor example to my students, the DPE, and Maintenance, so I admitted I has had been suckered into the kind of accident chain that I teach my student to avoid, and admitted I had knowing flown an unairworthy airplane. Incidents like this help to reset my level of tolerance for unairworthy item in aircraft, which was pretty high to begin with, but I allowed some outside factors to affect my judgement. When someone does start asking question, I need to be able to truthfully explain why I did what I did. If I start saying, “if anybody asks”, it is time to re-evaluate what I am doing.

As pilots we are given a lot of reponsibilty with little supervision. This is why the FAA is so harsh in penalties when they think pilot comprises their integrity. Their thinking is if they can’t trust you with small things, they can’t trust you with big things.

I know a CFI that had all if his rating revoked when the FAA found a fraudulent Transponder entry in his Aircraft Log. The CFI claimed he was unaware of it and his partner was responsible, The FAA argued that as a CFI (professional pilot) and an aircraft owner he was responsible for knowing all entries were legitimate.

Aborting the flight with a known, airworthy condition was absolute the right thing to do. Not only does a break the link in a possible accident chain, It can stop you and the CFI from potentially having to answer some uncomfortable questions about what happened.

A reputation for integrity is easy lose and difficult to earn back once lost.

Brian
CFIIG/ASEL

 

[James331]

You’ll probably be fine

I wouldn’t fly it

 

[LongRoadBob]

To the OP, I am also a student pilot, and am damned impressed with you having the sense and guts to go against the CFI on this. I hope I would too in that circumstance. More so, I would have hoped your instructor would have done the right thing and not put you in that position.
Again, I'm only a student, but I have studied the carb icing graphs in ground school, and there is a big range of temoeratures where icing can occur. It explicitly mentions summer being no guarantee about keeping ice free.

I don't know it is for other students, but a number of times we do or don't do things I had come to expect we ought to. Preflight inspection where I find something, but get the reply "that's ok, it looks like it's been there a while" etc, where I just take it for granted that it is right. The one I fly now, seems to never be all there. Pilot side door, upper hinge is missing, baling wire in it's place, the baggage door won't lock, is duct taped shut. Landing light not working.

Anyway, I think you did great and showed great attitude and resolve.

 

[LongRoadBob]

Also, what is the right thIng to do then? I mean after the decision to return.

I know in most cases the carb heat on means the engine is getting "unfiltered" air, which unless I misremember, is not good for the engine on the ground where dust, particles, gravel, etc. can enter in.

Would it not be best to immidiately cut the engine and push it back to the hangar?

 

[luvflyin]

Hi, I am a student pilot with very low time. Today was my third flight and during the runup the carb heat knob pulled out much farther than normal and there was no drop in engine RPM indicating the linkage had broken or become disconnected. My instructor seemed OK to still fly the plane as it was a very hot day and we shouldn't really need it. I figured if it is on the checklist and fails, don't fly. We taxied back and did not fly because I didn't trust it, did I make the right call? Also, should I be billed for the hobbs time we were in the plane for something like this?

Yes. Unless it turns out that you did need it, then no. Good call making a decision. No you shouldn’t be billed. Did they?

EDIT: My answer don’t make sense. What I was trying to say is there may be a time I would do it. I think you absolutely made the right call and are to be commended for your ‘Aviation Decisision Making’ and not being swayed by your passenger even though he was a CFI. I hope he gave you the credit you deserve

 

[luvflyin]

ok, scanned quickly through the thread but to lazy right now to actually read it. What’s the Verdict? Is it ‘legal’ or not?

 

[Tom-D]

ok, scanned quickly through the thread but to lazy right now to actually read it. What’s the Verdict? Is it ‘legal’ or not?

I'd say it could be legal when 91.405 and 43.11 were complied with.

91.405 Maintenance required.
Each owner or operator of an aircraft—

(a) Shall have that aircraft inspected as prescribed in subpart E of this part and shall between required inspections, except as provided in paragraph (c) of this section, have discrepancies repaired as prescribed in part 43 of this chapter;

(b) Shall ensure that maintenance personnel make appropriate entries in the aircraft maintenance records indicating the aircraft has been approved for return to service;

(c) Shall have any inoperative instrument or item of equipment, permitted to be inoperative by §91.213(d)(2) of this part, repaired, replaced, removed, or inspected at the next required inspection; and

(d) When listed discrepancies include inoperative instruments or equipment, shall ensure that a placard has been installed as required by §43.11 of this chapter.

IMHO I'd not fly it.

 

[Skip Miller]

ok, scanned quickly through the thread but to lazy right now to actually read it. What’s the Verdict? Is it ‘legal’ or not?

What do you think? What would you do, other than ask SGOTI?

 

[GeorgeC]

IMHO, it's not enough to just decide something is not needed and mark it INOP. You must also ensure that the fault cannot cause a secondary failure. That's not from the FAR, that's from a paranoid pilot who is an engineer who has led numerous failure investigations for missile flights.

Had a similar thing happen to me. Started up, engine ran rougher than I'd ever experienced before, shut down. Do it again, same thing. Third time, it started smoothly. Taxied to hold short line, did runup, started running rough again, so I limped it back to the tiedown. Very glad that it happened at 0 AGL on runup and not at 100 AGL where you get to pick which tree you wish to land in.

Strongly suspect that something came from together in the airbox.

 

[luvflyin]

What do you think? What would you do, other than ask SGOTI?

What do I think? First guess is not legal. What I would do other than what I did, asking SGOTI, is look it up myself. Probably wouldn’t have driven down to the Library to get all the references so I would have done it on the internet by GUIFTA(googling until I found the answer.)

 

[Skip Miller]

What do I think? First guess is not legal. What I would do other than what I did, asking SGOTI, is look it up myself. Probably wouldn’t have driven down to the Library to get all the references so I would have done it on the internet by GUIFTA(googling until I found the answer.)

First guess is correct. Looking it up yourself is a f=good move, earning you extra credit! But now your tolerance for these exceptions comes to the fore... Would you fly with a burned out position indicator bulb, if you were planning a good Wx day VFR flight? I would, and have done so. Technically illegal, but most of us would go fly. So the decision is yours. It is that PIC thing again...

Happy flying!

-Skip

 

[PaulS]

Hi, I am a student pilot with very low time. Today was my third flight and during the runup the carb heat knob pulled out much farther than normal and there was no drop in engine RPM indicating the linkage had broken or become disconnected. My instructor seemed OK to still fly the plane as it was a very hot day and we shouldn't really need it. I figured if it is on the checklist and fails, don't fly. We taxied back and did not fly because I didn't trust it, did I make the right call? Also, should I be billed for the hobbs time we were in the plane for something like this?

No, you shouldn't have to pay for the airplane, it was broken. The instructor, maybe, at least for the hobbs time.

 

[Dan Thomas]

Carb heat normally fails in the off position. It's a cable connected to a flap below the carb that changes the intake air flow from filtered air to heated air from the exhaust.

It can fail in any position, and if it fails when on it costs heap of power, more in some airplanes than in others. There are friction devices on some airboxes to hold the valve in position, and if the cable breaks as you pull it out, it's on for good. And if it's on or drifts on during takeoff you could be in real trouble.

Carb ice can happen at any temperature up to 100°F, if the humidity is high enough. Too many instructors don't understand carb ice and they pass along their ignorance and errors to the student. Seems that everybody trusts the instructor and doesn't read the textbooks anymore. Is reading really that much work?

If the carb heat control came out farther than normal it can indicate that the valve plate came off the shaft but the cable is still connected. A disconnected cable can often be pulled all the way out of the panel. All three or four feet of it. If the valve plate is off the shaft it can jump up and block the intake altogether and shut the engine down. It happened last summer to a fellow I know. Old airplanes that aren't well-maintained...

 

[FlySince9]

no!

 

[luvflyin]

First guess is correct. Looking it up yourself is a f=good move, earning you extra credit! But now your tolerance for these exceptions comes to the fore... Would you fly with a burned out position indicator bulb, if you were planning a good Wx day VFR flight? I would, and have done so. Technically illegal, but most of us would go fly. So the decision is yours. It is that PIC thing again...

Happy flying!

-Skip

Gotcha. Was just wondering what the ‘legal’ answer was. I’m gonna let it rest with my Kudos to the OP’s decision

 

[eman1200]

I haven't used carb heat in almost a year.

 

[SkyDog58]

In regards to payment, your CFI should pay you for the lesson in good ADM.