Pivotal Altitude

[rframe]

I heard supposedly it's a maneuver to simulate getting yourself out of a box canyon. But if you're the kind of person flying into those in an Arrow I'm not sure you need a Commercial certificate in the first place.

Actually it's based on an old school air to air combat maneuver. As you pass the bogey head on you want to turn quickly and get the high line, trading energy for altitude. So, you can see why it's a very valuable maneuver for the Commercial SEL pilot, particularly when the Piper Arrow is equipped with the factory optional 20mm Vulcan cannon.

 

[Mike H]

Mike H said: ↑

Or you could calculate it ahead of time... during the pre-flight briefing, for instance

"100x100/11.3=885, so lets start out at 900 agl and see how much we need to climb or descend throughout the maneuver"​

That is the point.

That's how I teach it, but it's not quite how I was taught in my commercial training.

 

[Roger Roger]

I heard supposedly it's a maneuver to simulate getting yourself out of a box canyon. But if you're the kind of person flying into those in an Arrow I'm not sure you need a Commercial certificate in the first place.

I'd have to defer to guys with more mountain flying experience than I, but I think it's not even really all that effective for that. I want to say that I read somewhere that you want a max G-load turn (somewhere around 70* bank for the 3.8 Gs a normal category aircraft can handle) at Va.

 

[JordanD]

The only one that makes sense to me is the power off 180. Because the only time an engine is going to fail is downwind abeam.

If i ever experience an actual engine failure abeam the numbers the first thing I'm doing is stocking up on lottery tickets.

 

[rframe]

I'd have to defer to guys with more mountain flying experience than I, but I think it's not even really all that effective for that. I want to say that I read somewhere that you want a max G-load turn (somewhere around 70* bank for the 3.8 Gs a normal category aircraft can handle) at Va.

Sort of...

A chandelle is not really the right manuever in a canyon because you're starting the turn too fast. In a canyon you dont want to start the turn fast and bleed speed through it, you want to start the turn slow because turn rate and radius increase/decrease exponentially with speed. Further, if you're dealing with rising terrain, which is a common gotcha for canyons, you may want to climb through the turn with the power to spare, but doing it like a chandelle where you're ending up at Vmc with maybe a few hundred feet between you and the trees and rocks is probably not a great idea, especially when you're also possibly dealing with a high DA.

Best to slow down (quickly with a power and flap dump if needed), to say Vref (1.3Vs/Vso) in a light single, then a nice controlled 30-45 bank and you'll feel like you're kissing your own tail on the way around. If it's a big canyon you could do Va, but then you're really just doing a normal turn.

I wouldn't recommend a steeper turn in a canyon unless it's to keep from immediately hitting a wall in front of you because of the inherent loss of SA that's going to occur with an extreme attitude when there is no horizon to reference.

Mathematical turn radius:

30-degree bank
70kts (753') vs 90 kts (1,245') vs 110 kts (1,861')

45-degree bank
70 kts (435') vs 90 kts (719') vs 110 kts (1,074')

 

[Houston]

I heard supposedly it's a maneuver to simulate getting yourself out of a box canyon. But if you're the kind of person flying into those in an Arrow I'm not sure you need a Commercial certificate in the first place.

You definitely heard the answer most people give during their CFI test. The follow-on question is if you were faced with a granite wall in a box canyon, would you do a chandelle. At that point the CFI candidate stops for a while and then says "heck no".

The reason I mention this is I always have that bad feeling that someone will stumble into just such a bad situation and think that a chandelle is the best maneuver to perform. It is better than nothing, but when push comes to shove, we can all get an airplane turned around in a tighter space than a chandelle uses.

For the most part, there isn't much practical application to any of the maneuvers. However, it is like the time I was talking with a well known aviation educator and I said "who the heck does 8's on pylons in real life". His answer was perfect. He said "everyone who wants to pass the commercial test".

 

[Mike H]

I tried to make the same argument about long division in the 4th grade.