Mountain flying

[Cessna driver]

So i'm sure most instructors teach the canyon or box canyon turn when flying in the mountains. Does anyone teach doing hammerheads in something like a 172?

[Cat Driver]

Why would they teach those turns?

[Beefitarian]

Under powered? Check.
Wrong fuel system and tanks? Check.
Potential for hitting a mountain? Absolutely.

You could phone around and ask I suppose.

[Colonel Sanders]

Where does this insanity come from? Why would
you want to try to kill yourself, doing a hhead in
a 172? They actually do very nice hheads, but
you will kill yourself if you try.

Recalling from first year calculus:

radius of a turn = velocity squared / acceleration

it might occur to you to do a turn at minimum
velocity, to minimize radius. Using bone-crushing
acceleration (say, +12 G's) in the turn isn't going
to work for a bunch of reasons.

[photofly]

Minimum turn radius is at Va, pulling the g limit.

[Cat Driver]

While we are on the subject of not killing yourself what possible circumstance would require such a turn in the first place.

[BibleMonkey]

Does anyone teach doing hammerheads in something like a 172?

Oh sure.
Try Luke 21:36

If the Good Book throws yer weight and balance off , just print this checklist and stick it by the yoke with some gum:

" O God, great and omnipotent judge of the living and the dead, we are to appear before you after this short life to render an account of our works. Give us the grace to prepare for our last hour.

All things whatsoever ye shall ask in My name, shall be done unto you; I beg of Thee, O Lord, for Thy holy Name's sake, to grant me at the hour of my death full consciousness and the power of speech, sincere contrition for my sins, true faith, firm hope and perfect charity, that I may be able to say unto Thee with a clean heart: Thou have redeemed me, and if I had bought a motor sickle instead, I never would have tried to hammerhead a 172 "

[Cessna driver]

Just curious, read some article this morning about down in the states someone was doing it. Thought it was just an american thing. Im not actually going to teach students that, nor try and teach myself it, but i was just curious.

[PointyEngine]

Minimum turn radius is at Va, pulling the g limit.

From memory turns at Va commence as a maximum rate turn, as the airspeed bleeds off (assuming you're in an under powered trainer) the turn will progress from a maximum rate, towards a minimum radius turn. Minimum radius would be to commence the turn at the lowest possible airspeed, for example with flap from what you might call "a bad weather configuration". Some countries teach the "max rate" turn maneuver, where you roll into the turn at Va, 60deg Angle of bank and power to maintain a designated speed while sitting just above the stall buffet. Sounds suicidal, especially when you're close to the ground, but as an emergency escape maneuver would be my go to choice, as the max you'd want it through 180deg. Not the kind of thing you'd want to go practice at low altitude, or without someone who is experienced alongside.

www.caa.govt.nz/safety_info/GAPs/Mountain_Flying.pdf‎

[Cat Driver]

The bad weather turn in the mountains is known as the terminally stupid turn.

Only the terminally stupid get in such a situation.

[BibleMonkey]

Just curious, read some article this morning about down in the states someone was doing it. Thought it was just an american thing. Im not actually going to teach students that, nor try and teach myself it, but i was just curious.

I understand, I've seen the similiar discussions of flying non aerobatic trainers past the poh.

There are some Bob Hoovers , and there are some experienced pilots that post here, ( who give far more constructive input than my almost never- serious posts) that can make airplanes do amazing things and not hurt them.

There is , I think , a larger number that survive physically unharmed, possibly wiser , but strain the airplane , perhaps invisibly reducing its lifespan .
And in spite of my earlier unserious post of a plea for a happy afterlife, I can"t help thinking that while there are 7 billion humans or so, there"s only a few thousand Cessna 172s.........

[photofly]

Minimum radius of turn is reached at Va, pulling the rated load factor.

Proof:

Recalling from first year calculus:

radius of a turn = velocity squared / acceleration

that's the inward acceleration only; we have to add the constant downward acceleration (1g) of gravity, at right angles, to get the total load factor g. So:

radius = v^2 / (9.81 * g_inward) [SI units]

g^2 = (g_inward^2 + 1) [Pythagoras]

rearranging:

radius = v^2 / 9.81√(g^2 - 1)

clearly we can reduce the radius (at constant v) by pulling a tighter turn and increasing g, up to the point at which the aircraft stalls. At the stall:

g = v^2 / v_s^2 [from the lift equation]

Substitute to get

radius = [ v_s^2 /9.81 ] . [ g / √(g^2 - 1) ]

v_s is fixed. When g is very close to 1 the radius becomes very large; close to the level stall speed you have to make a very wide turn to avoid stalling. By inspection, the turn radius is minimized when g becomes large; it tends to a limit of v_s^2 /9.81 (v_s in SI units)

Clearly to avoid breaking the aircraft the largest g allowed is the specified maximum load factor. As mentioned previously the optimal speed to fly (in terms of minimizing the turn radius) is the one which reaches the stalled condition at that g, which is the definition of Va.

If my arithmetic is correct that means you can turn a C172 in a radius of about 200 feet at 110kts if you're prepared to pull 4.4g, and at a bank angle of 77°. A 180-degree turn would take about 7 seconds, if the engine was strong enough to keep the speed up.

QED.

[sky's the limit]

And this ladies and gentlemen, is why I left airplanes.... Wow.

[Lurch]

The bad weather turn in the mountains is known as the terminally stupid turn.

Only the terminally stupid get in such a situation.

Exactly

I also think anybody teaching them is equally stupid. I have taught numerous people to fly in the mountains and not once have I taught such an idiotic maneuver. When flying in the mountains the key is to avoid flying in an area where such a turn is required.

Flew with a pilot recently who had a "Mountain" check with an instructor who taught them to always fly on the sunny side of the valley. well I guess I'm not that shocked I already knew how stupid the instructor was/is.

I'm not going to further acknowledge the stupid question about a hammer head. Except to say you are probably confusing them with a lazy eight.

Lurch

[PointyEngine]

+1 Cat, if you find yourself in a situation where a minimum radius vs max rate turn will dictate if you have a beer tonight, you've really stuffed up somewhere...

[digits_]

...

If my arithmetic is correct that means you can turn a C172 in a radius of about 200 feet at 110kts if you're prepared to pull 4.4g, and at a bank angle of 77°. A 180-degree turn would take about 7 seconds, if the engine was strong enough to keep the speed up.

QED.

With this you assume you are staying level. If you allow room to lose some altitude, I am wondering if it might not be able to get tighter (and with this I means the projected horizontal turn radius, not the vertical one). In the limit case you could say to do a split s, but a little bit less extreme I was thinking of more than 77° bank, while allowing the aircraft to descend, and thus stay at the limit of eg 4.4g.

Or, stay at 77° but limit to eg 2g and descend, to maintain the same radius as calculated above. Just an idea, or would that be a suboptimal solution anyway ?

A split S might not be the smartest move in a c172 (don't know, never tried it), but high bank angle + height loss sounds possible to me.

[Colonel Sanders]

A split S might not be the smartest move in a c172

Yes, it's even more dangerous than a hammerhead. And
the idea of giving away altitude rapidly in the mountains
(and converting it to excessive airspeed) pretty much
guarantees a fatal outcome.

I think someone mentioned a lazy-8, which is an FAA
Comm flight test maneuver. For a minimum radius
turn, you could consider half of a lazy-8 which is called
a wingover. Far less dangerous and violent than a hhead
or split-s. Pretty boring, actually.

A wingover is a 180 degree turn where you convert
your airspeed into altitude and perform a co-ordinated
turn. It is symmetrical, and you exit at the entry
altitude. You can use up to 90 degrees of bank at
the apogee quite safely, with the ball in the center.



I recall an exact dulplicate of this discussion on USENET
rec.aviation about 20 years ago, before Geoff Peck did
the Big Split. Plus ca change, plus c'est le meme chose.

[photofly]

Or, stay at 77° but limit to eg 2g and descend, to maintain the same radius as calculated above. Just an idea, or would that be a suboptimal solution anyway ?

That won't work, for two reasons.

Very little of the g-load in a turn that tight is provided by gravity, so starting a descent won't help you very much. If you pulled the same turn in outer space (110knots, 200 ft radius, bank angle now 90° for any turn) the Colonel's stated formula applies exactly and you must still be pulling 4-point-something g.

The second reason is more prosaic: the idea of this manoeuvre is to avoid rising terrain ahead; presumably you're not too far AGL and you don't have much height to play with.

[LousyFisherman]

So i'm sure most instructors teach the canyon or box canyon turn when flying in the mountains. Does anyone teach doing hammerheads in something like a 172?

Nope, I don't know how to do any of those. And judging by the responses the only people here I would trust in the mountains are Cat and Lurch. Maybe BibleMonkey . The Colonel would have to have a mountain checkout first:)

If you need to use a standard 30 degree steep turn to escape YOU HAVE ALREADY FSCKED UP!
If you need to use one of the above turns there is a good chance you are already dead, you just don't
know it yet.

And no amount of math will save you.

I had a mountain check out to rent a 172 once. I would not let that instructor fly my C150 in the mountains, his
solution to everything was more power.Needless to say, if the 172 is underpowered, the 150 is a nose heavy glider

Of my grand total of 190 hours, 85 of them are in the mountains

YMMV
LF

[digits_]

If you need to use a standard 30 degree steep turn

Huh ? Is 30° of bank a steep turn

[Colonel Sanders]

The Colonel would have to have a mountain checkout first

Flew once in the mountains, just south of Leadville,
Colorado. Don't know anything about it, didn't like
it very much. This place, I was at 7500MSL after I
landed:



If you want to do it, I might suggest two afterburners
to simplify things.

[esp803]

I'm a little shocked at some of the reactions to the idea of teaching minimum radius turns for exiting a boxed canyon.

Yes, if you have to do one, you F&*#ed up somewhere. Clearly I am a lesser pilot then some because I have made mistakes (although never requiring this particular solution), but I like to have every tool at my disposal to save my ass when I do make a mistake. Should we also not teach spin recoveries? I think you have to F$%# up pretty bad to enter an unintentional Spin. Not everybody out there has 20,000+ hours and the decision making that comes with that much experience. If a safe exercise like a minimum radius turn saves one persons life who otherwise would have died, I'd say it's a worth while cause to teach it. If someone scares his/herself in a boxed canyon it will greatly increase their understanding in avoiding such situations in the first place.

As to the OP's questions. Most here have given pretty good reasons on why you should not do aerobatic moves in tight mountain spaces. The fastest airplane I have ever flow through (low level) the mountains is a caravan, and even those are capable of remarkably tight turns when needed. I always keep either extra airspeed or altitude (or preferably both) to bleed off just in case. This should go without saying, but, don't get yourself into these situations in the first place... but if you do F&%^ up.... Know how to get out.

E

[iflyforpie]

I do Rate One turns in the mountains... flying at 8,000 feet through 7,500 foot passes surrounded by 11,000 foot peaks. If I have to increase my turn rate, something has gone wrong.

The best aid for turn radius is reducing speed. If you are getting into tight quarters, about 2000RPM, 70 knots, and ten flap for a 172 and 18" MP, 80 knots and 20 degrees of flap for a 182 work nicely. We don't GARA about turn rate in the mountains.

To do a canyon turn requires vertical space to maneuver. If you have the space to maneuver above you (free of cloud), why weren't you flying at a higher altitude in the first place? Unless it is a true box canyon, terrain generally gets wider as you climb higher. If it is a box canyon, you don't go into it unless you are sure you can either a) turn around comfortably in it with the above methods... typically in less than half of the canyon or b) that you are guaranteed to make it out the other side (no obstacles, narrowing, weather, rising terrain).

[Cat Driver]

The bottom line is if you get yourself in a situation where you have to perform an aerobatic maneuver to turn around in the mountains because you do not have enough space for a normal turn then I guess the Immelmann would be safest.

[photofly]

This pilot could have made use of some advice, and that was in urban New York.

http://en.wikipedia.org/wiki/2006_New_Y ... lane_crash