Sorry Timothy. I sometimes forget that the point of internet forums is to win, not to exchange information.
Yes, this has been a fine example of that and a great shame. I put up a video of the reality of most engine problems in MEPs in order to further greater knowledge and understanding than is shown by many pilots, and people want to prove that they “win” an altogether unnecessary argument about something completely different.
But I am glad that that has now been resolved and we are all on the same page now.
Am I the only one who cannot decipher some of the irony or cynicism in this thread?
For example
Engine fails in a twin. There are no consequences. No fatalities. No claim. Just a maintenance bill.
may apply to most failures in cruise (maybe not where an exhaust pipe comes off and the hot gas burns through the wing spar) and expertly handled failures on departure or arrival. Not the rest, for mismanaged assymetric flight kills loads of pilots.
But even enroute failures can kill in IMC – see e.g. this as one potential case.
may apply to most failures in cruise
Actually this is a threat area which is not covered that adequately in the ridiculously compressed six hours of EASA MEP training. Quite a few MEP accidents following engine trouble (and in 80% of the BE58 sample where an engine failure led to an accident there was a morbidity/mortality), the crew/pilot failed to carry out a precautionary shutdown, the malfunctioning engine then seizes and you are unable to feather the propeller. While a stopped propeller has less drag than a windmilling propeller, it still has more drag than a feathered propeller. Timothy is correct that in an MEP, precautionary shutdown is standard procedure, but not usually (read never) examined in the annual proficiency check.
You therefore do get accidents where there is a CFIT as the MEP drifts down as it fails to feather. In fact one of the BE58 events was an accident of this nature. You also need to have drift down escape routes planned as typically for normally aspirated MEP the SE service ceiling is below MSA and almost certainly MEA.
Also most MEP autopilots are not able to cope with asymmetric flight, and will be notified as such. Perhaps the Altimatic and S-Tec are approved for the PA31, but am not aware this is the case for other types. So in IMC the workload increases and you have a risk of loss of control events. Fortunately the IR renewal ride does cover EFATO and OEI approaches so a current pilot should be able to cope, although it isn’t difficult to come up with examples where this isn’t the case.
Finally the run of the mill MEP without engine fire suppression systems has the interesting design flaw that an uncontained fire will get to the main spar within two or three minutes. I am only aware of the FAA (and only for the ATP ME add on ride), requiring competence in an emergency spiral descent under instruments for this scenario. They also require a precautionary shutdown in the check ride. And yes the NTSB has examples of MEPs losing the wing due to uncontained engine fires.
Taking the thesis from the thread title one can assert that yes the second engine will take you to the scene of the accident if you either fail to carry out a precautionary shutdown and the engine can no longer be feathered, or you are flying in terrain where the MSA is above the SE service ceiling.
Of course there are some accidents resulting from engine failures in MEPs.
But what I object to, and this is all I have been saying from the start, is the ridiculous assertion that the second engine is there to take you to the scene of the crash. That is true in a tiny minority of cases; in the vast majority it takes you in a completely controlled and unhurried way to a suitable runway with engineers who can then get you on your way.
I agree with most of what Robert says, all wise advice.
There is one matter that probably deserves further discussion, though. If an autopilot is not certified for use OEI, does that mean that we don’t use it?
This is a kind of debate that I find myself in increasingly. Other examples can be found in current threads, for example on lookout, CAP 1122 approaches and unpublished approaches.
Yes, there are risks in using an autopilot under uncertified circumstances, but do those risks exceed the risks associated with the pilot having to focus on control rather than monitoring, diagnosis and planning? I suspect not.
Personally, if I lost an engine in IMC, once I had got it settled down I would definitely want to re-engage the autopilot so I could focus on diversion, fuel management etc. I would be aware that the autopilot might mask fuel imbalance, and would occasionally disengage it to check that everything felt ok, but then re-engage.
I can see how others might want to go by the rules and hand-fly, and that is their choice, but I don’t think that they would be best serving themselves and their passengers.
There should be a name for this argument – about the acceptance of some risk to alleviate others – so we can trot it out without full explanation. Something to do with clean needles or condoms might be most memorable.
Why exactly would an autopilot not work in OEI?
I know nuffink about twins (my twin total time is 1.5hrs) but I hear that – in an old twin, not in a bizjet with the two engines close to the centreline – one flies something like 7 degrees wing down, in order to maintain a heading with the ball centred. A normal AP isn’t going to do that; it is set up for wings-level. How is the OEI capability implemented, in the ones which support it?
Airborne_Again wrote:
Indeed! Of course insurance companies are really good at statistics. That’s how they make their living.
Interestingly a King Air is a much higher Hull premium (expressed as a percentage of Hull Value) than a CJ.
Peter wrote:
Why exactly would an autopilot not work in OEI?
In the two types above the autopilot works fine and use is SOP in an OEI situation.
I hear that one flies something like 7 degrees wing down, in order to maintain a heading with the ball centred
You hear completely and utterly wrong!
If I took you up in my aircraft, simulated OEI, set the rudder trim to alleviate forces and handed you control, I would challenge you to know that we were OEI.
Look at the video at the head of this thread. Where is your 7°?
I wish people would desist from spreading this kind of disinformation. You know that it will now appear on Flyer or PPRuNe as fact, because you wrote it, right?
Timothy, no need to get aggressive. I wrote I have 1.5hrs ME and know nuffink about ME. Also I couldn’t care less what happens on the other sites; I virtually never post on them.
PA31 AFM specifies 5deg bank towards operative engine if there is a failure during climb after take off. Once in level flight the ‘requiement’ Is no longer there.
DA62 AFM specifies that best OEI performance in level flight is achieved with 3-5deg of bank, ball not centred.
There are lots of very sound aerodynamic reasons for banking towards the live engine.
