Engine coughs and splutters: What do you do?

[TheFlyingSquirrel]

You're cruising along in a SEP and donkey coughs and splutters big time...lot of yaw...fearing an engine failure you enter auto. You have a bit of height to play with and the engine hasn't stopped. You notice T&P's in green and engine idling as normal. You wind up a little engine RPM to check response - seems to be OK. Do you risk bringing the power back in at altitude, or go for a flare with power recovery to an IGE hover ? Or, simply go all the way with the auto ?

Thanks guys.

TFS

[paco]

Try bringing in power, but don't leave yourself in a bad position - you might get a good landing out of it. One thing's for sure, I wouldn't continue the flight. Just make sure you land near a pub (for the engineers).

I had just that situation at night in the Alton Towers helicopter when the N1 gauge went - I entered auto and completed the landing in that case. Had I been higher I would have applied power.

Phil

[remote hook]

If you have the hieght to experiment, go ahead, you don't want to Auto if you don't have to. Access the situation to the best of your ability, and make the appropriate decision when you have as much information as you can get.

RH

[Fun Police]

i'd agree with paco, and try to bring throttle up and use whatever power you might get at the bottom to assist with landing, just make sure your feet are ready for whatever yaw you might have to deal with.

[vorticey]

how do you know it was the engine? maybe turbulence, lack of oxygen in the air over a fire, or even water in fuel? if temp and press in the green id pull in power and asses the engine again. if nothing happends keep flying, if the same thing happends and the engines still running id use it at the bottom just cause you can.
p.s. i have no idea what a sep is but assume its an engine:ugh:

mick

[Fun Police]

i suppose that might be true but when it actually happens would you like to make that much of an assumption? no one would fault you for landing and having it checked out. it's your a$$ that the machine is strapped to.:ugh:

[helmet fire]

What is an SEP??? A single engine piston? But then paco talks N1 gauge, so maybe it means something else? BTW paco: what sort of aircraft gives you all those indications (coughing, yawing, etc) from a N1 Gauge failure?

In the scenario TFS paints for a turbine single, I would carry out the compressor stall checklist for that particular type. For a piston, I would curse the day I gave into my fear of them and found myself in one!! But I might suspect one of a million things: spark, fuel vapourisation, water in fuel, intake block, carb icing perhaps?? None the less, I would wind the throttle on to test return of power: if power was available I would be flying to the nearest clearing, if not, I would be autoing to the most suitable terrain.

[paco]

Sorry, I was in a rush - it was a Longranger, and on the 206, you will get the engine failure audio if the N1 gauge goes below 55%, even if the engine is actually working. I meant to say that I was in a similar situation with a possible engine problem from one that was possibly working, if you see what I mean. I didn't get any coughing, except from the passenger in the back!

Given the height, I would still try to see what power I could get and attempt a controlled landing, before an auto. Having got on the ground, maybe keep it running for a while to see if it happens again?

Phil

[TheFlyingSquirrel]

sorry guys - fixed wing terminology - Single Engine Piston was intended.

Thanks for the replies.

[PPRUNE FAN#1]

I am always amazed at how helicopter pilots seem spring-loaded to the engine-failure mode and are willing to actually roll the throttle off and enter autorotation for any old reason. Two pilot-friends of mine admit to having done just that (and one of them did it twice!). Um, hellooooo...cross-check anyone? Me, personally, I don't roll a throttle off unless the engine is surging badly and my feet can't keep up. Never even been tempted. If anything, I roll it *on* harder just to make sure it hasn't slipped back and that's what's causing the prob. (Had that happen a time or two.)

One day, in the middle of a sightseeing tour in a 206 ("SET", I guess) the engine-out horn started blaring and there was a red light somewhere up on the dash. Woke me right up, it did! My left hand, which was occupied either picking my nose or scratching my arse (I can't remember which) was nowhere near the collective as usual. By the time I got it there my eyes had found the N2 tach: Situation normal. What the...? Look around...ah so, N1 gauge failure. Pull the "Caution" breaker and continue the flight. Heart-rate slowly returns to normal.

Fellows, here's a piece of advice from a guy who's been around the block once or twice. It is worth exactly what you've paid for it, so treat it accordingly: DO NOT ROLL THE THROTTLE OFF UNLESS YOU SEE THE NR HEADING SOUTHWARD!! Or unless the airplane is on fire. There, I've said it and I feel better. "Fly the aircraft" does not mean "Autorotate the aircraft any time you think you might be having a problem." I mean, come on.:*

[cl12pv2s]

PPRUNE FAN#1,
I agree with you to a certain extent...multi engine and singles (with high inertia systems), then yes, there is a time where you can cross check systems and trouble shoot...possibly finding that maybe autorotation is not the answer.

However, it's not so easy to be as cool in a low inertia single engine, where even a cough is going to cause a fluctuation in Nr!
I would hate read of an R22 pilot who heard the Low RPM horn go off, and decide to 'remember what PPRUNE FAN#1 said' by launching into a troubleshooting exercise and then getting into a worse situation.

With altitude below me, I would much rather:
be in autorotation without needing to be, than;
not be in autorotation as my blades start to stall!

Again it depends on the aircraft you are talking about....when you get indications of an engine failure in a simple 'SEP' such as a R22 or 300CB, it is likely because you have engine problems!!! Whereas, the more complicated the aircraft systems, there are more reasons for horns and bells to go off without being anything to do with the actual engine.

It also depends on your experience...a newer pilot will not have the experience to fall back on in order to make a 'quick' and effective assessment of a situation.

So PPRUNE FAN#1, while I do agree with you in part, pilots who have 'been around the block' must be careful with the messages they may be inadvertantly imparting to 'greener' pilots when writing on these forums.
Green pilots...as PPRUNE FAN#1 says, FLY THE AIRCRAFT AND MAINTAIN NR.
As to Flying Squirrel's original scenario. Depends where....
Generally try to bring in power and try to fly it....many times a cough is just that...a cough. Be wary throughout the flight and maintain forced landing options and altitude.

The critical decision is when to decide whether to make an Engine off Auto or to try a normal landing. It is impossible to say here what to do. It depends on your individual circumstances. I have been in situations where I have elected to fly back home after a cough...I have also been in situations where I have elected to get down to a hover and play with the thottle at 5 feet. I definatly would not try an auto to a hovering power recovery. Either use power all the way down (that way you know you have it) or decide not to use it at all.

(if over really crappy area or forced into autorotation) concentrate on maneuvering to the best forced landing site. Use any power you can out of it, but making that site should be priority. REMEMBER to hold the throttle detent to off. The last thing you want just as you touch down is another cough!

[the coyote]

I was flying an R22 at night and the engine suddenly started running rough, it wagged the tail, manifold pressure went right up and RRPM began to decay. I immediately entered autorotation and within a few seconds realised that the engine was now running fine. I smoothly brought the power back in and flew it another 10 minutes back to base uneventfully, albeit pumped on adrenaline.

I didn't at any stage roll of the throttle. (TFS, why would you do that - "you wind up a little engine RPM.." ? Roll off throttle only if you NEED to, and I saw no need to roll off throttle in this situation.)

My immediate thoughts were carby icing. (It turned out that the carby had come loose, and I presume when I lowered the collective the reduction in manifold pressure kind of sucked it back onto the intake manifold.)

Time slows down, but it was instinctive to assess how much power the engine was still producing. I don't even remember thinking about it, just doing it. Maybe the fact that it was night helped that instinct. No one in their right mind elects to auto an R22 (especially at night!) if there is an alternative, in my opinion.

A forced landing is exactly that, do it when you ARE forced to. Otherwise stay in the sky until you can assess the best course of action, in my opinion.

[PPRUNE FAN#1]

cl12:I would hate read of an R22 pilot who heard the Low RPM horn go off, and decide to 'remember what PPRUNE FAN#1 said' by launching into a troubleshooting exercise and then getting into a worse situation.Whoa. 'Alf a mo'. Look, let's all admit that flying helicopters not "easy" in the way flying planks can be easy. Even in cruise flight, helicopters require more concentration and attention than any aeroplane. If something goes wrong, the RRPM can go south in a hurry. Okay. We accept this, we understand it, and we prepare for it.

There is ONE gauge on the panel that take priority over all others: the rotor tach. F*ck everything else, rpm is life. Even if I'm flying low down the beach, checking out the birds and not looking anywhere near the panel, if I hear a low-rotor horn, I don't have to do any immediate troubleshooting, I LOWER THE COLLECTIVE and pull back on the cyclic! It's automatic, intuitive, no need for discussion or thought. They put the low-rotor horn there for a reason; I'll use it, thank you very much.

I don't immediately slam the stick to the bottom and I do not roll the throttle off at this point...at least, not for another moment. At the same time, I look at the tach to see what the rotor rpm is really doing. I do this quickly because, all joking aside, RRPM is the *one* thing I'm not a slacker about. When checking the tach, if I find out that it is indeed low, then the pitch goes all the way down. "Something" caused that and needs troubleshooting. If the horn is blowing but the rpm is still up in the green, that's another thing.

My point is that pilots, in their rush to do "something" many times react inappropriately, and too many times are spring-loaded to roll the throttle off when a simple reduction of collective pitch is what is really called for.

[Thomas coupling]

Pruney: I'd wager a tenner that the R22 fraternity call your bluff - time is revs in an R22....1.3 secs did I read somewhere? About half the time it took for you to get your hand from up your a*se to the collective.....

You obviously haven't flown an eggbeater, then?

:E

[Buitenzorg]

OK, let’s back up and look again at the symptoms as described:

- Single Engine Piston: almost by definition, low rotor inertia. Even a Bell 47 would only give you several seconds to get the collective down rather than 1-2 in an R22.
- Engine coughs and splutters: this is not good, whatever the cause.
- Lot of yaw: either a (partial? temporary?) power failure (nose yaws left) or a tail rotor (drive) failure (nose yaws right).

Both power loss and tail rotor (drive) failure require immediate action by the pilot. The nice thing is that the immediate action in both cases is: collective – lower; so you don’t have to work out which is the problem (power or tail rotor).

While I have some sympathy for those who advocate “check and make sure before you do anything”, if you have either of these problems for real, and do nothing for several seconds while you check, you will die. Simple as that.

On the other hand, if you immediately enter autorotation, point it at the best landing spot, and then check and experiment, you have all the bases covered. Indication problem? Add power and climb away. Serious trouble? Complete the auto to the ground. Not sure but you have (some) power and control? Land anyway and check it out – unless the spot is so bad (slope, growth, surface, obstacles etc.) that you’re sure a safe landing is out of the question.

If you make an autorotation to practically any place, and arrive at 5 ft AGL with the RRPM in the green, very likely everyone will walk away, even if you roll over or hit something in those last 5 feet. Contact terra firma out of control, and odds are somebody will be hurt badly or worse.

One last thing:
DO NOT ROLL THE THROTTLE OFF UNLESS YOU SEE THE NR HEADING SOUTHWARD!!
If you see the NR heading southward ROLL THE THROTTLE ONWHILE SIMULTANEOUSLY LOWERING THE COLLECTIVE as should have been drummed into you by your instructor! Remember the Robinson training video showing an R22 dropping vertically with the rotor stopped? This will be you if you roll the throttle off in a low RPM situation! In the same video Frank explains why. Watch it (again)!!!

[nigelh]

I had engine cough and yaw in AS 350 a few times, turned out to be damaged turbine blades and fuel surge, never once felt like winding off throttle or going into auto ! I would set up a gentle approach to open area and just maintain rotor rpm...ie if you HAVE to lower lever to keep rpm you do , if you dont ...you dont . Dont forget that in the cruise you have all the extra time to lower lever by just doing gentle flair to maintain rpm. Had engine failures in Bell 47 , in that case you have time to get the manual out before you drop lever.....and if you dont like the spot you have autoed into you can lift her up and move her a few feet !!:ok: I hear that in Russia they dont really dwell on autos ,as more people crash from either practicing them or just blindly entering auto for no good reason ie horn,warning light,strange sound etc etc

[PPRUNE FAN#1]

Thomas Coupling:Pruney: I'd wager a tenner that the R22 fraternity call your bluff - time is revs in an R22....1.3 secs did I read somewhere? About half the time it took for you to get your hand from up your a*se to the collective.....

You obviously haven't flown an eggbeater, then?If by "eggbeater" you mean "R-22" then no, I've never flown one. If I ever did, with what we know now about the microscopic time between "engine splutters" and "rotor stops", then I would have my left hand super-glued to the collective and wouldn't be using it for any other cockpit duty such as scratching my arse. Fortunately, the day of my N1 gauge failure, I was in a 206 which is slightly more forgiving of such transgressions.

Folks, my only point is that pilots are too spring-loaded to "enter autorotation" by rolling the throttle off. Bottoming the pitch does the same thing. There are some (well, a few) things in a helicopter that allow you to sit there and think about them. Rotor rpm is not one of them. The proper response to *any* problem is almost never "roll the throttle off" and you can almost never go wrong by just leaving the dang thing alone. If my engine started "coughing and spluttering," rolling the throttle off and entering auto would not be *my* first response. But hey, if you want to commit yourself to a power-off landing (over where? wind from where?) without doing a couple of other things first, that's fine by me. Idiots.

I am really, really starting to believe that some of you self-anointed "experts" on this forum got all of your experience from reading AFM's and have no earthly idea what it really takes to fly helicopters safely.

[Buitenzorg]

PPRUNE FAN#1

Completely agree with your last post:ok:

Especially pilots are too spring-loaded to "enter autorotation" by rolling the throttle off. Bottoming the pitch does the same thing
If I misunderstood the drive of your earlier post, my apologies.

[overpitched]

I have had the very problem you are describing a while ago in a B47 and I am happy to run through what I did at the time and you can pick it to pieces if you want.

I was 3 up in a B47 over fairly big timber at about 6-700 agl. The engine started to surge and backfire and the aircraft was kicking around a bit. The only clear spot was to my downwind side and the wind was about 15-20 knots. If I went for the auto I would have had to terminate downwind as I wasn't high enough to get to the area and turn.

I lowered the collective enough to maintain rrpm and with the intermitant engine I had just enough height to fly a tight orbit and get the field into wind. I flew a fast approach as the engine was surging very badly and I thought it was going to quit totally. At the end I had enough power to just run it on at about 40 knots and once we were on the ground I cut the throttle back to idle and the engine stopped.

It worked ok at the time but I think every situation would be different depending on height, quality of landing spots etc.

[havoc]

Any one have a problem at looking at the MGT/TOT or what ever you have.

If the engine is getting cold its a out. Send a tach gen failure, cross checking TOT confirmed the engine was going fine.