We have to distinguish between solid aerobatic pilots in RV-8s and the regular guy who flies his family in his C-172.
In the RV-8 you could do a „half reverse cuban eight“ to reverse the course … or one of those extreme bush flying maneuvers, the most extreme one being a box canyon turn where you simply turn the plane around on the spot: full flaps before the stall, full left rudder and full power. Was shiwn to me by a professional bush pilot in a 300 hp Cub. But you don‘t recommend that stuff to „normal“ pilots.
Fly on the safer side of the valley, do not wait too long and until the valley gets too narrow to turn. Slow down, 10 flaps and fly a safe steep turn. If more bank is necessary lower the wing loading by descending in the turn. This will work for any but the most narrow valley.
When i was 12 yo my father flew into a dangerous box canyon in Austria, too narrow to turn and made an unannounced emergency landing on a military grass strip. He was greeted by soldiers who only relaxed when they found out that the base commander was some distant Austrian relative. He got some fuel from them and he took of in the other direction. Guess how many times i had to listen to that story :-) But that was the Seventies …
You are thinking too much Mk2. It’s not engine power that pulls you up in a loop, it’s speed. Orographic turbulence – the aircraft has no idea what kind of turbulence it is, and doesn’t care. I don’t have a GoPro, and never have, but maybe I can find some glider videos with loops from ENOP. No engine power at all and doing loops in the middle of “orographic turbulence”.
Seems to me everybody are thinking too much. The main “rule” of mountain flying is don’t hit the mountains. Otherwise it is simply business as usual, only energy and wind management is more important than in the flatlands. You make turns in the usual way, just remember the main rule. If you happen to bump into a situation where you cannot make a normal turn, but need to make a turn nonetheless, and this isn’t planned up front, then this is an emergency situation. You are in deep shit in fact, caused by bad planning and poor airmanship, some call it bad luck though. Anyway, in such situations you do whatever the aircraft is capable of doing to get you out. If that is an immelmann or a hammerhead or whatever, who cares? If the aircraft has a BRS, then this is the time to use it, if you have the alt.
What’s wrong with an Immelmann in a sunny valley with orographic turbulence, high density altitude and not enough engine power to pull you from straight & level up through the top of the loop… yeah I really don’t see what could go wrong there in fact. @LeSving maybe you want to post a video of you doing it to illustrate?
An Immelmann in a situation where turbulence is possible, and accuracy is essential? I’ve little aerobatic experience, and none at low level, nor in turbulence. Not something I’d try.
I’ve often done turns in glacial valleys, often encountering turbulence.
Climb close to chosen side, allow speed to reduce, bank and let nose drop. Pull out as speed increases, not pulling much G. As Adam said earlier.
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?
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”…
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.
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
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.
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.
