Twins - engine failure / EFATO (merged)

Brilliant! I can’t wait to see Timothy at the British nationals in Peterboro this summer:)

Perhaps, we have time for the MEP crew to work up a nice formation display routine, with alternative engines being failed in a synchronised fashion, perhaps to the strains of Mussorgsky (Night on a bald mountain).

A OEI lightly loaded PA31-350 might boast 15lbs/HP, so vertical penetration may not be quite to the standard of a CAP232 or SU-26. C/R propellers might need some new techniques for gyroscopic manoeuvres, although OEI hammerhead turns might prove a comparative advantage when turning away from the live engine.

I would go easy on the negative Gs, the engine mounts might not have been designed for this, nor the oil and fuel system. The Shrike was certified in the Utility category, while the PA31 might also have to go a bit easy on the positive Gs, the CAA used to time limit the spar to 7500 hours. I believe they were silent on how many of these could be aerobatic.

Fuji_Abound wrote:

I do wonder how accurately a sim can replicate this type of stuff – I mean can the programmers really do the science to that degree.

I dont mean that the aircraft will not do it as Bob has so well demonstrated, but is the sim realistic?

Timothy uses X-plane. That software computes the effect of airflow over the aircraft starting from first principles so it should be quite realistic.

Fuji_Abound wrote:

Does that give it the ability to compute how the wing would perform upside down and with an asymetric engine then? It is a serious question, and genuinely interested, although it might seem otherwise.

As far as I understand, yes. In fact, X-plane was initially developed not as a general purpose flight simulator but to predict behaviour of experimental aircraft designs (thus the name).

See https://en.wikipedia.org/wiki/X-Plane_(simulator)#Flight_model.

Fuji_Abound wrote:

Does that give it the ability to compute how the wing would perform upside down and with an asymetric engine then?

Both seem separately pretty realistic, yes. Obviously not something I have tried in combination for real!

“Does that give it the ability to compute how the wing would perform upside down and with an asymetric engine then? It is a serious question, and genuinely interested, although it might seem otherwise.”

If you try benchamaking XPlane vs PoH on few aircrafts under various inputs, appart from popular GA aircrafts, the numbers (climb rates, cruise speed, stall speed, takeoff distance..) are way different

My understanding X-plane uses realistic physics for “airflow models” behind the scenes so it should be good on medium speeds subject to accuracy (putting aside stall/turbulence on slow speeds and compressibility on high speeds), in the other hand how realistic the specific aircraft model is really hit and miss except on popular types…

There are huge numbers of aircraft on the market, nearly all created by third parties. Some are excellent and some are crap. Carenado is a good manufacturer and I am impressed by the Chieftain (bearing in mind I fly about 200 hours a year in PA31s).

Obviously the models are only as good as the people who put them, but X plane uses a very different approach than most other sims, using real aerodynamics instead of table run airplane modelling. Austin Meyers is maybe one of the very few people in this field who really understand what these sims do (one of the others is Simon Hradecky of the Aviation Herald) and he has maybe gone further than most in this regard. I’d say, if a sim is capable of really simulating these issues, it probably is xplane.

The main reason is that the original idea of Xplane had nothing to do with a competition product to MSFS but it was targeted to a very different market, namely the experimental airplane builders. The idea was, that anyone designing his own plane would be able to “fly” it before the first piece of wood has been removed from the forest. Therefore, the approach by tables and flight data packages used for most full flight simulations was impossible to begin with. It was only at the Microwings conference at Dallas that Austin brought his new sim to a different audience and realized what potential it had. I remember him and his presentation vividly, a young boy he looked like then with a product which had the audience pay attention to. But even then, the real breakthrough in the entertainment industry only came when Microsoft decided to shut down their francise and with the introduction of smart phones, which now appear to be one of the main sources of income for Xplane.

But all that nonwithstanding, Austin has to my knowledge never really lost the primary objective Xplane was made for but listened to others how to make it sellable (pretty graphics and so on) with considerable success. I’ve flown some sims which are run by xplane and they are fantastic, the very best I ever saw being the Caravelle simulator at Munich but there are others as well. He also used the same engine for his Xavion app and I am quite sure he used a lot of his knowledge when he built his own airplane.. as far as I know most of the instruments in that plane are programmed by himself.

As to the Chieftan, how does the asymetric handling compare with real life, again especially at the edges of the envelope and beyond when insufficient rudder is applied?

It is pretty good. It would be better on a motion platform, of course, because, whatever we say and teach, a lot of asymmetric is about the seat of your pants. However, my gorgeous, pouting, uncomplaining bride might baulk at that suggestion

Rudder response through the Brunner pedals isn’t great, though I have worked very hard with them, so you need to pay more attention to the ball than in real life, but that’s a good learning tool.

Performance is a pretty good match. Add about 6” to what would be the ops normal setting and it’s fine. You soon forget that you are on one.