Debunking Glider Spoiler Turns Causing Spin Thinking

Either a large majority of us are unaware that we are on the verge of death every time we adjust our spoilers while landing, or some people are being taught this and causing them to unnecessarily fear spoilers and using them to their full degree of helpfulness and effectiveness.

Here's a video I made trying to demonstrate what happens when you use spoilers while turning...nothing! I was a little bit of a punchy mood while taking the video - sorry for being a little bit snarky.

https://youtu.be/tC-Yqp-uHo0

Here is the description of the video:
I had been flying gliders for almost 20 years before someone on the internet wrote to me that adjusting spoilers while turning to land can kill you. What?!?! Supposedly, because your inside wing is flying so much slower than the outside in a turn, a little spoiler can spoil the whole day. I have been freely adjusting my spoilers as needed during landing my entire flying career. Why have none of the glider manuals I have ever read warned about this?

I've asked multiple CFI-G's (glider instructors) and they are also baffled this is being taught to students. I've now heard from 4-5 different people (all pilots outside of USA) that have been taught this by their instructors. Time to try to debunk this. Glider is an ASW-27B flown dry at the time of this video out of Cedar Valley, Utah.

Thanks for your insights and comments to try to help clarify the confusion.
Bruno - B4

I've never heard of this. YGTBSM!
17 years flying gliders, 12 years as an instructor, moving the spoliers at will, turns or no turns, no problems.

I've never read anything in any glider flying manual, FAA handbook, or aerodynamic study.
Better warn the airlines, no spoiler actuation during turns!

I love to do a flight review with some of those pilots and watch them when I use the spoliers.
BillT

In Australia there is a definite fear of using the blue handle during turns in the pattern (circuit).
Seems unjustified to me.
Jim

On Monday, June 1, 2015 at 10:12:22 PM UTC-6, Bill T wrote:
I've never heard of this. YGTBSM!
17 years flying gliders, 12 years as an instructor, moving the spoliers at will, turns or no turns, no problems.

I've never read anything in any glider flying manual, FAA handbook, or aerodynamic study.
Better warn the airlines, no spoiler actuation during turns!

I love to do a flight review with some of those pilots and watch them when I use the spoliers.
BillT

Wait and you will see. I am already starting to get pilots defending this on the comments section of the video! That's why I brought it up. Wait till Europe wakes up tomorrow, sees the video and starts commenting. Should be very interesting!

Bruno - B4

I can't remember the last time my airbrakes were closed during a final turn in a high performance glider - and I live in Europe.

Hi John,

If you're having to use the airbrakes everytime have you considered opening
up the circuit? Or is there something at Portmoak that prevents this?

I'm quite happy to use (or have my pupils use) airbrakes during final turn
if they were using them on base leg. Less happy for pupils to open them
during the turn. The final turn probably takes about 5 seconds so why not
wait 'til wings are level and the picture has stabilised before opening the
brakes. Why increase the workload for the sake of a few seconds?

KN

At 06:26 02 June 2015, wrote:
I can't remember the last time my airbrakes were closed during a final
turn
in a high performance glider - and I live in Europe.

It is all about speed, attitude and banking.

When you are flying with high alfa, close to stall and then deploy brakes trouble are not far away.
If you fly in correct speed (1,5x stall + ½x wind) deploying brakes are safe. As long as you not change attitude and speed (glider specific behavior) when the brakes goes out.

South Africa appears to follow the "no spoiler during turns" rule as well.
On two occasions I was told by instructors not to use spoilers/air brakes while in banked turns onto base or onto finals.

Once was during a 30 degree bank to finals at 120km/h (64 knots) in an Twin Astir at about 300 feet AGL with spoilers half extended.
I deliberately flew faster to compensate for the increase in G-loading and loss of lift due to the spoilers being half out but it wasn't an acceptable answer to the instructor so I adjusted my flying style.

The "no spoilers during turns" rule makes sense if you're flying the turn too slowly and not taking the increased stall speed into account.

Example: According to the POH, a 650kg (1430lbs) Twin Astir stalls at about 90km (49 knots) with spoilers fully deployed. Add a 45 degree bank and the stall speed increases to 126 km/h (68 knots).
This is usually above the normal approach speed flown during circuits so I can conceive that a pilot who is not "ahead of the glider" could possibly fly too slowly during the turn. Throw in an uncoordinated turn and things could go wrong very quickly depending on glider type.

Maybe those grey beards have merit in their reasoning however the use of spoilers during turns closer to the ground can certainly help with altitude control during off field landings where there isn't a 1000+ foot runway available and there may be obstacles that can only be avoided with a turn to very short finals (e.g. high voltage power lines blocking the approach to a field and the field is too short to go over the top of 55 meter (180 foot) high power lines).

"In Australia there is a definite fear of using the blue handle during turns in the pattern (circuit).
Seems unjustified to me.
Jim "

I have flown in Australia for some 15 years, instructing for the last six, yet I have never heard such nonsense. Sure if you are very slow pulling g and then open air brakes, you may have problem, but that problem stems from the slow speed.

Paul

At 08:44 02 June 2015, Paul B wrote:


"In Australia there is a definite fear of using the blue handle during
turns in the pattern (circuit).
Seems unjustified to me.
Jim "

I have flown in Australia for some 15 years, instructing for the last
six,
yet I have never heard such nonsense. Sure if you are very slow pulling g
and then open air brakes, you may have problem, but that problem stems
from
the slow speed.

Paul


I have heard of problems changing flap settings in aborted approaches ,but
I always thought the increased wing loading steadied every thing and
increased aileron response.
It is probably prudent to leave the brakes where they are during the turn,
then sort out the approach on the old "one thing at a time " theory, but I
would be reluctant to shutting the brakes for the turn then opening them
after.