Greetings, 

I have a pilots license and was wondering how accurate twin engine performance is modeled on xPlane.  Specifically at VMC and slower.  Most likely real pilots would be best to answer this question especially those with multi engine ratings.

 

Happy New Yearr.

@cbreezeHappy New Year!   Why not download the XP12 demo and try it for yourself.   You will have a Baron and King Air to check out.  SEL INS here - not close to current LOL!  

cbreeze - well versed in XP12 and RW flight. Think I have experienced it but not deliberately induced VMCA. In reality it is rudder authority dependant. Bigger the rudder more control when your assymmetric.  Not a factor in heavy like the B737 because of closeness of engines to fuselage and lack of yaw with engine failure - you stall before you get to Vmca due to weight! So off to see for myself in XP12. Worth a look at!

The answer is YES it does. I tested this with the Thranda BN2A which is of high fidelity in terms of sim handlng and performance - that is close to RW, So the answer is in the BN2 VMCA (which by the way is not in the manual) is 38 knots. You will get stall warning horn on about 58 knots (correct) and with one idling not feathered yaw can be managed holding a very high AoA or pitch attitude until 38 knots or quickly below the 40 kt mark - this in accordance with the data I have and the aircraft could not be prevented from rolling to the critical or failed engine until the nose was pushed down, control recovered and VMCA exceed back to say 65 knots. So it was an accurate demonstation of the sim capabilities. Yes it will simulate VMCA correctly. 

Note if trying this with other aircraft or models - VMCA can be very high in some twins due to small rudders. I key to good VMCA behaviour is the XWind max for the type in the case of the BN2 it is a very healthy 55 knots of crosswind which tells you this aircraft had good rudder authority - which it did! You will not find a flapped speed for VMCA as generally it is neither given nor know - you can work it out - but adding flap does not lower the VMCA but on the contrary raises it significantly - so the BN2 VMCA if flap was at TO setting was 85 knots thats right twice the speed of no flaps. 

Trick is never to put the aircraft in a configuration that will invite a demonstration of VMCA some like the PA30 will roll quickly inverted then nose down in a flash! The BN2 was a very docile aeroplane - so as for the sim accuracy - tick that box!

Good morning.

Thanks to all that responded.  I got my multi in a twin Comanche many moons ago.  Have about 30 hrs in a Seneca.  Haven’t flown a twin in a very long time and was trying to dust the cob webs off.

There have been a lot of fatal  accidents lately involving twin engine aircraft. Mostly involving the loss of one engine during various phases of flight.  Or crashes doing VMC instruction.  The instructor friend who got me my rating was killed in 1976.  He was working with a student on his multi and did a VMC roll on takeoff in July of that year.  That was in a twin Comanche and he was a very experienced instructor in that Comanche which he owned.

Thanks again and fly safe.