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Are slower turns necessarily tighter in radius?

What is a “full stall turn”?

The Americans use the term hammerhead stall which is perhaps more accurate. In fact no stall should occur during a stall turn, as the aircraft approaches zero G in a zero lift angle of attack vertical climb, the stall speed approaches zero – if lift and g was present, kicking in rudder might result in a spin/gyroscopic departure.

As your recovery altitude is lower than your entry altitude, a stall turn, would not be my recommendation for any emergency manoeuvre in a box canyon. Most mountain flying courses teach avoiding getting trapped in a box canyon, not using a wingover to exit.

Oxford (EGTK), United Kingdom

Agree with Adam.
But the downwind, downdraft, side of ridge may also be the sunny, updraft side. Your decision. Sun/ shade is much more important in Utah/Colorado, with dry ridges and strong sun, than in Scotland, with wet or snow ridges and weaker sun.
Be prepared for turning in turbulence.
A hammerhead in a narrow valley, going into turbulence, looks suicidal to me.
A descending turn, with increasing speed, is my usual narrow valley turn.

Maoraigh
EGPE, United Kingdom

This has been a very interesting read. I used to think that the tightest turn is the slowest one, though my instinct is to never fly that slowly so e.g. the turn in that video was done at c. 100kt. My Va is 130kt but to make the best use of that I would need to be pulling something like 3G.

Of course the other thing one should do is first turn towards the other “mountain” so as to make more room, but in this case there was circuit traffic so one had to more or less fit in with that.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

Of course the other thing one should do is first turn towards the other “mountain” so as to make more room, but in this case there was circuit traffic so one had to more or less fit in with that.

As any mountain course will show, you normally already should be flying really close to one of the sides of the mountain. (It might sound disturbing at first), so there shouldn’t be room for you to turn towards the mountain.

RobertL18C wrote:

The Americans use the term hammerhead stall which is perhaps more accurate

The jargon tends to be different, and the maneuvers are executed differently depending on time and space and aircraft. But the basic idea is to turn 180 degree without eventually loosing alt and/or speed (energy) and without extending it out in the horizontal plane when thinking about valleys. The most “gentle” way of doing it, is probably doing a Lazy eight kind of turn, pulling up while gently rolling/yawing slightly above stall speed at the highest point, where also the actual rotation in yaw is largest (although googling a Lazy eight, they are often executed rather different than I am used to). A step further is a wingover, a “stall turn” kind of maneuver in the vertical, although the aircraft describes an arch in the vertical, and it is not really stalled. The next step is a real stall turn, or hammerhead stall, where the rotation in yaw is done at nearly zero speed, thus the rotation axis is near the center of the aircraft.

It depends on the aircraft. With an RV, you could as well do an Immelman, since it can be initiated well below normal cruise speed.

The elephant is the circulation
ENVA ENOP ENMO, Norway

Peter wrote:

I used to think that the tightest turn is the slowest one,

and for practical purpose I think you were right before…

The table posted before disregards, the effects of pilot error and ability to apply and maintain a precise bank angle, AoA and speed.

for example at 45 degree bank, how accurately can a pilot hold the bank angle AND angle of attack AND Speed, compared to 60 or even 70? and what effect does those variations have on radius and altitude…

In particular if the table had a columns to account for variations in AoA and Speed from the ideal.

Last Edited by Ted at 26 Sep 09:50
Ted
United Kingdom

Yes, the table is a bit academic ;)

In practice, what i’ve been taught is 30 angle of bank, with 30% margin over stall speed (so going slow). It’s also worth noting that when you are in a valley, you don’t see the horizon, so doing your turn will be more difficult (and you don’t really want to just have your eyes “inside”.

As to how close to the side of the mountain:
+youtube+sMuOZd7CRyw?t=3!m1s

Last Edited by Noe at 26 Sep 10:05

Noe wrote:

what i’ve been taught is 30 angle of bank, with 30% margin over stall speed (so going slow)

Sound smart, even better with flap and gear.

Just as example, using this http://www.csgnetwork.com/aircraftturninfocalc.html

lets say I attempt 30 AoB at 84knots (Vs+30%), but I execute 35AoB at 90knots (9% speed increase) I get a radius of 1029ft.
as opposed to an attempt at 60AoB at 110 (Vs+30), I execute 52AoB at 120 (about the same speed increase and bank error) I get a radius of 1001.2

Sure these are a bit contrived, but it’s my observation that these errors aren’t too wide of the mark.

None of these calculations allow for the distance to establish a turn.

Last Edited by Ted at 26 Sep 14:16
Ted
United Kingdom

Immelmann, hammerhead turn in a canyon… this thread is becoming more and more interesting.

Worth of note – the ideas have been confirmed with google, so, paraphrasing Jackass, “these evasive manouvers have been practiced on the internet by trained stuntmen, don’t try this in flight”…

Shorrick_Mk2 wrote:

Immelmann, hammerhead turn in a canyon… this thread is becoming more and more interesting.

IMO, I have only read and heard of people being trapped in a “boxed” canyon when the main factor was a low ceiling putting a lid on things. In those situations things tend to end up very bad anyway. It’s a bit late to start solving the situation when you already have your arms and feet tied, you are blindfolded any minute and the water is reaching your neck. In other cases, in a nice valley and the sun is shining, what’s wrong with an Immelmann?

The elephant is the circulation
ENVA ENOP ENMO, Norway
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