Some Multi-engine questions

[Nate26]

I just successfully completed my FAA checkride for Commercial AMEL. I got kinda beaten up on one portion of the oral and Im struggling finding some good references to strengthen my understanding prior to my ATP and MEI rides.

Computing Accelerate stop and Accelerate go distances with a 1959 Piper Apache PA23-160. If you have never seen one of the old Piper owner's manuals, lets just say it is not user friendly. There are no tables for ASD or AGD. I remember reading in the flight handbook that ASD can be computed by adding takeoff distance and landing distance plus 20%. But I had no clue how to figure the AGD, and just had to swag a number that included a climb to 50 feet at Vy plus 20% I passed, but Im not exceptionally proud of being caught out here.

Any tips?

[Mach E Avelli]

Don't feel bad. You applied common sense and while your numbers are probably not accurate, they would be safely on the conservative side. I would not have thought of adding the 20%, so well done there!
Old light twin aircraft like the Apache were not certificated to any proper performance standard that we would accept today. The second engine was more a perceived safety device than an actual one.
When you start your ATP studies you should get proper and representative flight manuals to work with. Then you will have real numbers.

[john_tullamarine]

There are no tables for ASD or AGD because there was no requirement for the OEM to produce or provide such data

ASD - an extremely conservative calculation .. but that's fine.

Accelerate go distances with a 1959 Piper Apache PA23-160 ? Probably not relevant to real life ... perhaps even a non sequitur .. I did my initial twin with a very experienced TP (thanks Hugh) on the Apache .. for the OEI stuff, I flew the aircraft and he operated the "failed" engine sufficient to preclude our killing ourselves.

I suspect that your calculation would be non-conservative ..

Under both 6000lb and the traditional 70mph/61kt maximum stall speed a light twin is basically a single with half an engine on each wing ... see, for instance, FARs 23.66 (http://www.ecfr.gov/cgi-bin/text-idx?SID=d2d3a10f13fec9d9b8f8a17cb01cbfbf&node=14:1.0.1.3.10.2.60.17&rgn=div8) and 23.67 (http://www.ecfr.gov/cgi-bin/text-idx?SID=d2d3a10f13fec9d9b8f8a17cb01cbfbf&node=14:1.0.1.3.10.2.60.18&rgn=div8).

[Tinstaafl]

Accel-go for an Apache? That had me wondering. Why would you think that's an option in that type? Accel-go isn't a certification requirement** for the type. As JT mentioned, it doesn't even have to have +ve climb performance in an asymmetric clean configuration, let alone with gear/flap extended and a windmilling prop.


**Ignoring other regulatory jurisdictions that may impose more restrictive requirements - but then I'd expect charts to determine compliance.

[Mach E Avelli]

If the aircraft has no true accelerate-go capability, the FAA check airman should not be requiring candidates to compute it.

However, if it is accepted that at some point, even an Apache could fly at least with some small climb gradient on one engine, I suppose that point in the flight path could be said to be the accelerate go distance. Probably impossible at gross weight, but just achievable at some lesser weight.
Upon reaching 50 feet and assuming the gear is up and prop feathered, blue line speed reached - maybe that's what the examiner was really after to see if the candidate had a grip on the reality of flying a low performance twin?
At a guess with only two on board, that would probably have the accelerate-go somewhere around 3000 metres, so do-able from a major airport, but clearly not from your average county airstrip.

Of course, if one really did have the luxury of a 3000 metre runway, accelerate-get airborne and land/stop would probably be a better distance to have in mind! That one is not in Piper's books either. The marketing people of the day would not have wanted it.

[john_tullamarine]

At a guess with only two on board, that would probably have the accelerate-go somewhere around 3000 metres

.. that's height AGL, I presume ?

Seriously, I had lots of fun in the Apache (even took mum and the cat to Sydney for the weekend one time) but it's a single with half a flea power engine on each wing ....

[Mach E Avelli]

I also have fond memories of Apaches and early Aztecs. One even looked like an Apache, with a short nose. But they grafted a locker on to the front of it to make it look like a B model. It went well on two engines but if the left engine failed and stopped rotating, there was no hydraulic pressure to raise the gear. In theory, while flying along on the other engine, you could reach down and manually pump it up. As if.....
In reality, the better option would have been to stay heads up, not even try to feather it but simply find a good place to crash.
Were any of these beasts ever modified with two hydraulic pumps - or what would have been smarter- an electric/hydraulic pump?

[Tinstaafl]

Some Aztecs were modified with a 2nd hyd. pump, mounted on the other engine.

[justanotherflyer]

Of course, if one really did have the luxury of a 3000 metre runway, accelerate-get airborne and land/stop would probably be a better distance to have in mind! That one is not in Piper's books either. The marketing people of the day would not have wanted it.

One of the reasons why a wise early employer of mine prohibited operations from any runway length that didn't permit precisely such a short flight!