The 180-degree Turn

[kevinl4000]

If I may turn the question around a bit, consider taking off from a very short runway - obviously you aren't going to try a 180 and that option is off the table. Now consider a very long runway (such as might be at a former USAF base). If you're you're still "low" when the engine conks out you still have runway left provided you dump energy quickly. If you climb out at Vx and you're high enough when you cross the end of the runway a 180 should be doable even with the reaction time delay (Yes I know that a 180 is actually a 210 plus a reverse 30). Both are obviously good outcomes (and a reason to love long runways!).

So my question is, under light wind conditions, what combination of min. runway length and min. altitude AGL does the 180 back to runway become a viable option for the average pilot in the RV-12? Thanks for your input.

[BobTurner]

Remember there is not one best glide speed. No wind at gross weight is what is published in certified aircraft. Lighter weight, that speed comes down (like the square root of the weight).
Headwind? Go faster.
Tailwind? Go slower.

[Mich48041]

Is best glide speed actually the best speed for 180 degree turn? A slower speed during the turn will make the radius shorter and keep the plane closer to the runway. The minimum rate decent speed of 55 knots will keep the RV-12 in the air longer, giving the wind more time to blow the plane closer to the airport. Many people have been killed when an airplane stalls close to the ground. The stall speed increases when turning. It is better to monitor the AOA which is not affected by G-forces in a turn.
Joe Gores

[BCP Boys]

I think we would all agree that each airport is different and it's up to the pilot be aware of the airport surroundings at all times. There are several airports in our area where if you take off in one direction you have many choices straight ahead but taking off the opposite end gives you absolutely no choices and it might be worth the risk turning around depending on your altitude, speed, position, etc. Bottom line is it's good practice to know your plane and practice it's capabilities or lack of at different scenarios but if you continue to practice turning around at a particular altitude every time, odds are your engine won't remember that - Back to the glide speed, in my -7 the best glide speed was posted as 71 Knots when I bought it and for the most part it seems to be correct.

[David Paule]

Remember, in a turn you're pulling some g. Because of that, the minimum sink speed and max L/D speed both increase by the square root of the g.

The quickest turn is at the maximum g you can pull. That's why earlier I said it's not a steady state maneuver. You need to start with a steep turn and when you lose speed, make it shallower. But at all times you've got to maintain control.

It's kind of fun to practice this at altitude. You'll quickly get a feel for the various ways speed, bank angle and turn radius all work out. That said, Paul has it right: when it happens you've got to make a quick risk assessment and if you're critically low, probably the best thing is to go straight ahead under control.

One perhaps surprising possibility with a fast-climbing airplane and a headwind on the runway is that it's entirely possible, even likely, to complete the maneuver, roll out and find that you've overshot the runway. This is more than disconcerting, it can be fatal. I guess the phrase would be fatally embarrassing. You've got to use some judgement and not simply whip the plane into a tight turn.

You could easily be in a situation where if you turn now, you'll overshoot the runway, and if you turn later, you won't make it back.

Dave

[Lote]

Ideas to consider from the glider world, where we routinely practice the turn back to the runway from as low as 200 agl.

1) The optimum bank angle for least altitude loss v. rate of turn is 45 degrees. No more, no less.

2) Always turn into the cross wind for least displacement from the runway centerline.

The glider take off checklist includes 1) deciding before take off which way the turn will be if the rope breaks and 2) calling out 200 feet agl on climb out. The intention of both items is to get set mentally. If the rope breaks below 200 agl, you land straight ahead or make a partial turn either way to avoid obstructions.

We assume the rope will break (or the towplane engine will fail) on every take off.

The only difference for power would be the decision altitude.

[jrs14855]

There is some excellent information available on this subject. Charlie Precourt devoted his Sport Aviation column to this last month.
Article by Van in current Kitplanes, excellent article about a real life scenario.
Sunrise Aviation is based at John Wayne Airport, really no place to go to the northeast. They teach turnback to students. They also have an excellent video but I don't remember how to find it. You could call them and ask.
One thing I NEVER see mentioned is the benefit of a shallow turn at some predetermined altitude, say 200', on takeoff. offset in the desired direction and then turn back parallel to the runway. Now you are in a position to make a true 180 turn back to the runway. If there is a crosswind, simply let the airplane drift until you are offset the desired amount.
The numbers that Charlies article uses are 500' for a 90 degree turn, 1000' for a 180. These are generic numbers that will vary considerably depending on the airplane.

[Mike S]

Originally Posted by RV10inOz

Depends on which model you fly.

Well, this is posted in the RV 12 forum, and he lists what looks like a 12 series serial number......

[jrs14855]

The sunrise videos can be found at sunriseaviation.com/turn-arounds
Videos were done in a Cessna 172 to a remote airstrip, simulated takeoff and climb, simulated engine failure at 500' AGL.

[RV10inOz]

Originally Posted by Mike S

Well, this is posted in the RV 12 forum, and he lists what looks like a 12 series serial number......

And your point is?

The real point is take Paul Dye's post and compare it with mine. You can be in one camp or the other but never undecided.

In aviation if you only think you can....you can't. And this is PD's point exactly. Best to take plan A.

If you are Pierre Smith and have tested and practised, then you know for sure that Plan B is going to work, rather than just hoping it might.

Right now I need to go do some more practise as I am not current at the manoeuvre and my takeoff brief does not include it or the threshold at which it is available is higher. Today it is 700' and turn of the cross runway which is a 60 degree cross (the one in the video).

You need to know this before you roll. Always expect a failure and be pleasantly surprised when it does not.

DO NOT GO TRY THIS BY YOURSELF. YOU NEED AN EXPERT TRAINER. THAT MOST LIKEY IS NOT YOUR TYPICAL CFI.