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An unusual twin accident - fuel exhaustion?

This fuel saving issue seems strange. Maybe he simply wanted to visit someone, or do some extra flying, and used this fuel saving thing as an “excuse” to his wife or something.

I guess on a VP prop the rpm will not change?

Would the EGTs not give it away instantly?

I don’t think so. Especially as fuel starvation will first give an indication of rising EGT (as the mixture becomes leaner) followed by falling to zero. The EGT gages on many twins are hiden somewhere deep down on the panel because you really only use them for leaning in the cruise. If at all, because setting the desired fuel flow works quite as well. Very confusing and with no time to analyse the situation when on short final. The engine failure drill on twins does not bother to analyse the problem or determine which engine has failed. All levers go forward instantly, directional control is maintained and only when this is possible, the flaps are retracted to takeoff position and the gear is raised when positive rate of climb is achieved. Only thereafter, the failed engine is determined and feathered.

I think I have written about it more than once already, but my three engine failures on piston twins went like this:

#1: C421, max takeoff mass, magneto failure on climbout in IMC. One engine misfired so badly, that the resulting vibrations were such that reading the instruments was nearly impossible. We reduced thrust on both engines and got us vectored back to a landing at the departure airport. Workload did not permit an analysis of the engine failure and as both seemed to develop some power, we didn’t shut one down. We just continued with as low power as possible. We never found out which engine it was until after landing.

#2: Seneca III, climbout at around FL70, close to max takeoff mass. A valve rocker pin failed, leaving a valve stuck open through which the pressurised manifold air vented outside. This could be seen instantly from the MP gauge. Also, the engine was running on five cylinders only, but that was secondary to the low MP pressure and could not be determined from the instruments. Return to the field and landing was uneventful and we left both engines running.

#3: C421, lightly laden, turbocharger broke away from the exhaust manifold upon rotation. Even trough the vibrations and unusual noise the effected engine could easily be identified. Loss of MP and yawing (luckily still in VMC) was a clear indication. Reduction of power and leaning cured most of the vibations, but the climb rate was poor and with the aid of ATC we could do an 180 degree turn (over the live engine) for a landing in the opposite direction. Again, I kept the engine running which turned out to be wrong. Due to the ruptured exhaust, hot exhaust gases and flames had already caused damage inside the engine nacelle. I was told that at least eight fatal accidents with this series of aircraft have been attributed to exhaust ruptures, consequently igniting and blowing up the auxiliary tank in the nacelle or even the main tank inside the wing.

Last Edited by what_next at 16 Nov 13:26
EDDS - Stuttgart

Confirms my impression that heavily turbocharged engines tend to have much more mechanical failures than other engines.

Max, re #1: did you ever have the idea of cycling through the mags in order to see if that solved the misfire? I know this is written in some engine failure/engine trouble checklists, but by far not all of them. I would certainly do it if I experienced a heavily misfiring engine. Obviously it dedends if there is at least a little bit of time.

Last Edited by boscomantico at 16 Nov 13:31
Frankfurt (EDFZ, EDFE), Germany

Yes the go around/landing or whatever he was doing was mishandled but he just shouldn’t have created the emergency. Running out of fuel is completely avoidable and doesn’t just happen randomly. There are some risks that we can’t control easily such as what next’s exhaust failure. But we can make sure the plane doesn’t run out of fuel.

I have done plenty of long legs where I arrive with legal but low amounts of fuel. But I have a fuel plan, I monitor it, and if it isn’t going according to plan or the weather at destination is not going the right way, you land and get more fuel. I just don’t understand the thought process that gets people into this position.

EGTK Oxford

Max, re #1: did you ever have the idea of cycling through the mags in order to see if that solved the misfire?

No, there was absolutely no time to do troubleshooting of any kind. With hindsight, it would of course have been the easiest thing to just turn off the magnetos one at a time. But the emergency checklists of all twins that I have flown so far do not even mention the magnetos (other than turning them off after feathering the engine) so following the checklist we would not have been pointed in that direction. In a single, troubleshooting may save your day, but in a twin, you shutdown the bad engine and continue on the good one – finding the fault is left to the mechanics on the ground.

Last Edited by what_next at 16 Nov 13:42
EDDS - Stuttgart

Performance is marginal in some light twins…Seneca 1 is a shocker, for example…but is perfectly adequate in most light twins, certainly in the later Senecas, Baron, Aztec, PA 31 series and in the 300 and 400 series Cessnas.

This should have been a non-event, whether he opted for a go-around or land, but I agree that a go-around would be a bad idea, not because of performance, but because the other engine might have failed.

I have had quite a few engine failure in twins, and, of those, most have been fuel related. The trouble with a fuel related failure is that the engine surges, just as described in the report, meaning that it is impossible to identify from Dead Leg-Dead Engine. However, there is no doubt looking at the gauges, as one of the RPM needles will be all over the place, while the other is static.

On a wider front, with all the real engine failures I have had in twins, Dead Leg-Dead Engine has never helped once. I consider it merely as a technique for making life easier for test candidates and actually to be really dangerous if it’s the only weapon in the armoury when reality bites. It is far, far safer to make the judgement from the gauges.

The trouble is that there is no “engine fail” gauge on a piston engine, as there are circumstances which will allow any one of the gauges (ie MP, RPM, FF, EGT, CHT, TIT) to remain at pre failure levels, but there is no failure which will result in all the parameters remaining correct. I can assure you, after a lifetime of experience, that a quick glance will immediately reveal the failure, in one way or another.

So, I would beg people, once they have passed their MEP tests using the otherwise useless dead leg method, to only rely on gauges when the chips are down.

EGKB Biggin Hill

…. I have had quite a few engine failure in twins, and, of those, most have been fuel related.

Okay …

…but is perfectly adequate in most light twins, certainly in the later Senecas, Baron, Aztec, PA 31 series and in the 300 and 400 series Cessnas.

I did my MEP in a Seneca V, and the instructor that he would always recommend rather crashing it in a controlled way on the rwy or in a field than trying a go-around on one engine. He was a Piper salesman for decades (and a master aerobatic pilot and European Vice Champion in a Pitts in the 70s.

I know that under perfect circumstances is possible, but many times it’s not.

Last Edited by at 16 Nov 13:58

I just don’t understand the thought process that gets people into this position.

From my experience, mostly because refuelling is inconvenient for some reason. The inconvenience may be caused by high fuel prices, long waits at the fuel pumps, the wrong kind of fuel carnet or credit card accepted (this is one of the main reasons for fuel emergencies in commercial operations of light aircraft!) time constraints by expiring flight plans or slots, other students/renters waiting for the aircraft, impatient passengers, airfield closure time, etc.

I myself have been lured into some low-fuel states by one or the other points on my list above, but never to a point where it has become really dangerous (apart from the wrongly set fuel totaliser about which I wrote some weeks ago and where the low fuel state caught us by surprise as we were sure we had done everything right). During my last 6+ years flying Citations I have seen low-fuel lights just once. But that was anticipated, we had no passengers on board, the weather was CAVOK everywhere and we had working plans “B” and “C” if for some reason a landing at destination would not have been possible. Still it made me feel really unwell to see those lights come up.

Last Edited by what_next at 16 Nov 14:05
EDDS - Stuttgart

I have both performed and watched a lot of asymmetric go-arounds and, if done properly, they are not a problem.

It’s getting people to do them reliably properly which is the issue.

EGKB Biggin Hill
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