A2A Introduces the Accu-Sim Piper Comanche 250

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Dooga
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Re: A2A Introduces the Accu-Sim Piper Comanche 250

Post by Dooga »

Scott - A2A wrote:
ClipperLuna wrote:Odd question: According to the POH (and as evidenced by lack of a cowl flap selector on the controls screen), this plane has no cowl flaps. It also refers to setting airspeed on descent to "Maintain Cylinder head Temperature in Green." Does this mean you have to slow down a lot, a little, or hardly at all during your descent?
Good question, and yes, the #1 cylinder can get below the min CHT during descents in cold weather.

Scott.
Scott, any chance for a digital engine monitor gauge for this one? Pretty please? :)

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Nick - A2A
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Re: A2A Introduces the Accu-Sim Piper Comanche 250

Post by Nick - A2A »

Dooga wrote:Scott, any chance for a digital engine monitor gauge for this one? Pretty please?
A digital engine monitor would be great and I can see Scott used a couple of different types in the real 29P. However, I got the impression from the engine monitor thread in the C182 forum that the Accu-Sim per cylinder EGT/CHT variables necessary to properly model one don't exist (yet). Of course, I'd love to be proved wrong on this! :wink:

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Nick
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pilottj
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Re: A2A Introduces the Accu-Sim Piper Comanche 250

Post by pilottj »

I bet it is going to be released this coming Sunday. My birthday is next Monday the 22nd, and if I remember right, Captn Jake's is the day before mine, which would be Sunday the 21st. :D
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Tiger_Walts
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Re: A2A Introduces the Accu-Sim Piper Comanche 250

Post by Tiger_Walts »

ftrusky wrote:Looks like I better get some practice time in on my A2A Cherokee before this 250 is available to purchase.

Will it use the same fuel tank management arrangement as the Cherokee with a flipper?

Thanks.
I wanted to know how the tip-tanks operated as in FSE there are only 2 tanks in the plane spec (yet it still holds 90gal). What I learned suggests that there will likely be 4 fuel tanks specified in the aircraft config file. Fuelling the plane for an FSE flight isn't an issue as we have to load A2A planes manually. But any fuel not in one of the main tanks may not be counted by the FSE client as fuel remaining at the end of a flight.

The JL Osborne tip-tank mod replaces whatever arrangement you have in the cabin with 2 independent valves. One for the left wing tanks and one for the right wing tanks. These can each be moved to one of 3 positions: Closed, Main and Tip. There is a single fuel level meter for the tip tanks with a switch to select which tank you want indicated. Because you can only feed from one tank at a time on each wing, use of the tip tanks must be restricted to when flying straight and level to prevent fuel starvation.

The A2A Comanche may of course vary from this setup.

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Bruce Hamilton
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Re: A2A Introduces the Accu-Sim Piper Comanche 250

Post by Bruce Hamilton »

pilottj wrote:...Captn Jake's is the day before mine, which would be Sunday the 21st. :D
http://a2asimulations.com/forum/viewtop ... 15#p360259

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pilottj
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Re: A2A Introduces the Accu-Sim Piper Comanche 250

Post by pilottj »

Bruce Hamilton wrote:
pilottj wrote:...Captn Jake's is the day before mine, which would be Sunday the 21st. :D
http://a2asimulations.com/forum/viewtop ... 15#p360259
Thanks Bruce, I stand corrected, looks like Friday might be the day then...even better! :D
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hangar
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Re: A2A Introduces the Accu-Sim Piper Comanche 250

Post by hangar »

If it were me... having a business event such as this that could lead to potential issues of the day stealing away my full attention from my child's most important day seems like not the greatest of ideas. I'm sure Jake would understand since he is involved...but still...as a father I don't think I'd do it. I'd save it for it the day after at least.
Last edited by hangar on 15 Jun 2015, 18:16, edited 1 time in total.

VH-MAL
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Re: A2A Introduces the Accu-Sim Piper Comanche 250

Post by VH-MAL »

VH-MAL wrote:And here's a link to the POH for the A2A Comanche model:

http://brianmichael.org/n5448p/N5448P_POH.pdf

An interesting read!

Mal
I hope I didn't cause any confusion by putting this POH up. As I said, it is meant as an interesting read, and as an historical document.
Obviously there will be differences between what is described here and the "real" aircraft - the alternator being one!
That said, it is certainly whetting my appetite!

Mal

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Re: A2A Introduces the Accu-Sim Piper Comanche 250

Post by Dogsbody55 »

I would have thought that it will be released before Friday, since the release was announced as happening this week. Once it is released, there will be a flood of support requests and who wants to spend the weekend doing that, especially given Captain Jake's upcoming birthday.


Cheers,
Mike
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Re: A2A Introduces the Accu-Sim Piper Comanche 250

Post by Dogsbody55 »

AKar wrote:
Scott - A2A wrote:
ClipperLuna wrote:Odd question: According to the POH (and as evidenced by lack of a cowl flap selector on the controls screen), this plane has no cowl flaps. It also refers to setting airspeed on descent to "Maintain Cylinder head Temperature in Green." Does this mean you have to slow down a lot, a little, or hardly at all during your descent?
Good question, and yes, the #1 cylinder can get below the min CHT during descents in cold weather.

Scott.
The CHT issue as a whole makes a very interesting general topic, where actual reliability data, at least the anecdotal, tends to be buried under sample variance. For instance, let us ask: when is the CHT that is under a given green range lower limit actually harmful to the engine/cylinder?

I've had so many, mostly conflicting answers to that question that I stopped counting! :)

-Esa

Shock cooling is a real issue for air cooled aircraft engines. GA planes used for pilot training tend to suffer from this, with many a cracked cylinder being found on these planes. It's not surprising really given the amount of time spent doing circuits. It all depends on how quickly the throttle is closed, for how long, and what the CHT was before the throttle was closed vs ambient air temp. If your plane does have a cowl flap, you'd keep it closed during descent so from that perspective, that the Comanche doesn't have one is not important. There is no one answer other than to plan your descent so as to allow more gradual cooling of the cylinder heads and keep CHT at an acceptable temp range, as mentioned in the POH above.

To give what is today an extreme example of this, pilots of piston powered airliners were not allowed to reduce power by more than 3 inches of manifold pressure at a time, then wait for CHT's to stabilise before reducing another 3in MAP. So they had to slow before descending, and watch that manifold pressures didn't rise during descent while also watching their CHT gauges. There was a well reported exchange some time back (in the 90's I think) between the captain of an Air Atlantique DC-6BF and ATC. It seems that after crossing the Alps at 20,000 ft ATC asked him to descend to 12,000ft and maintain 200kn. He replied "I can either descend to 12,000ft or maintain 200kn. Which do you want?" Those old radial engines are remarkably fragile if mis-handled.



Cheers,
Mike
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AKar
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Re: A2A Introduces the Accu-Sim Piper Comanche 250

Post by AKar »

Mike,

That's correct but then again, there are some airplanes used to tow gliders for example that take about as much punishment this way as an engine possibly can, and many have relatively little trouble with their engines. Full throttle up and idle descend at just about maximum speed. Certainly shock cooling is not for good, but how bad it actually is, I believe depends on how good sample the individual cylinder happens to be, how evenly it is stressed by attachment maybe, and especially I think it matters whether it cools evenly which in turn depends on installation. It may be the biggest differentiating factor in between the engines: on what kind of installation they are used.

But the trick in the question was, when it is harmful to let the cylinder temps drop below that green arc? That is, even if we do that gradually. Does full power with relatively cool CHTs to start with cause accelerated wear for example? Shock warming? Maybe. :) I've heard arguments for and against.

It tells a one kind of story that often the engines that have CHT gauges and maybe cowl flaps are pampered and pilots strictly enforced to follow some methods to keep the temps at given range and the temp changes as gradual as possible, however, when the engines do not have those gauges, all that is mostly forgotten and more practical common sense steps in to the advices. If you can't see it, it doesn't happen! :mrgreen:

-Esa

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Scott - A2A
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Re: A2A Introduces the Accu-Sim Piper Comanche 250

Post by Scott - A2A »

If my memory serves me correct, Lycoming's min CHT temp is 165 deg. This is probably a good minimum to observe, as lower than this could result in clearances being too tight. The only time I've seen these temps is in extremely cold weather, up high, on descent, and on the #1 cylinder - nothing a baffle wouldn't take care of if you planned on doing a lot of these kinds of flights.

Also keep in mind, many modern cowling designs don't include cowl flaps.

Scott.
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Piper_EEWL
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Re: A2A Introduces the Accu-Sim Piper Comanche 250

Post by Piper_EEWL »

AKar wrote:Mike,

That's correct but then again, there are some airplanes used to tow gliders for example that take about as much punishment this way as an engine possibly can, and many have relatively little trouble with their engines. Full throttle up and idle descend at just about maximum speed.
I can reassure you that with tow planes (with air cooled engines and where I learned towing) the descent is not done with throttle closed and at full speed. CHT's are watched in the descent. And usually you will descend at the yellow arc but with some power on the engine so shock cooling isn't as big of an issue.

I agree with you though that on airplanes where you dont have a CHT gauge a lot of the correct procedures seem to be forgotten!
B377&COTS, J3 Cub, B-17G, Spitfire, P-40, P-51D, C172, C182, Pa28, Pa24, T-6 Texan, L-049&COTS, Bonanza V35B

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AKar
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Re: A2A Introduces the Accu-Sim Piper Comanche 250

Post by AKar »

Piper_EEWL wrote:I can reassure you that with tow planes (with air cooled engines and where I learned towing) the descent is not done with throttle closed and at full speed. CHT's are watched in the descent. And usually you will descend at the yellow arc but with some power on the engine so shock cooling isn't as big of an issue.
Likely not completely closed but at very low power - and many tow planes don't even have CHT gauges. It is an old topic, some pilots tend to fly more aggressively than others, and some of the others keep complaining about shock cooling the engines are subjected by the others. I attempted to steer clear of those conversations, and focus on flying at the other end of the rope knowing that I outglide them anyway when they break their engines! :mrgreen:

-Esa

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Piper_EEWL
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Re: A2A Introduces the Accu-Sim Piper Comanche 250

Post by Piper_EEWL »

AKar wrote:
Piper_EEWL wrote:I can reassure you that with tow planes (with air cooled engines and where I learned towing) the descent is not done with throttle closed and at full speed. CHT's are watched in the descent. And usually you will descend at the yellow arc but with some power on the engine so shock cooling isn't as big of an issue.
Likely not completely closed but at very low power - and many tow planes don't even have CHT gauges. It is an old topic, some pilots tend to fly more aggressively than others, and some of the others keep complaining about shock cooling the engines are subjected by the others. I attempted to steer clear of those conversations, and focus on flying at the other end of the rope knowing that I outglide them anyway when they break their engines! :mrgreen:

-Esa
:mrgreen: I like that end too
B377&COTS, J3 Cub, B-17G, Spitfire, P-40, P-51D, C172, C182, Pa28, Pa24, T-6 Texan, L-049&COTS, Bonanza V35B

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