Debunking Glider Spoiler Turns Causing Spin Thinking

On Tuesday, June 2, 2015 at 9:47:56 AM UTC-6, Dan Marotta wrote:
That's a pretty good $0.02, Bill.

There's a trend to teach people to stay out of trouble by being overly
conservative rather than to teach proper theory and practice.
Disappointingly this leads to a bunch of mediocre pilots and, I believe,
more accidents.

As to using dive brakes, I open them as I begin my final turn (a
descending 180 deg turn to final) and I use them during the turn as I
see fit. Once on final I use them less, maybe 1/2 to 3/4 until just
before touchdown when I open them fully. I pick my touchdown point on
downwind and fly to that point. Never do I fly to a landmark and then
make a turn to base, fly to another landmark and turn to final. That's
just asking for trouble.

My $0.02.

On 6/2/2015 8:51 AM, Bill D wrote:


On Monday, June 1, 2015 at 9:09:34 PM UTC-6, wrote:


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.

On Tuesday, June 2, 2015 at 11:48:56 AM UTC-5, Bill D wrote:

When watching the video I grimaced when I saw the spoilers open on downwind and base on every landing even though the glider was well below normal pattern altitude. In this situation, the spoilers should remain closed until the glider is stabilized on a short final approach.

It's fascinating reading about all the different ways people are taught to land gliders.

I was taught to check spoilers on downwind (so you can adjust if either the lock full open, or don't open at all), then about abeam the touchdown point, pull on 1/3 to 1/2 spoilers (depending on how effective they are) and fly the pattern, trying to not change spoiler setting until landing. BUT - If low, less or close, if high, more and slip. In my LS6, I set the flaps to landing (or less, if the wind is strong) on downwind and don't worry about them anymore until after touchdown.

I also like the military style "180" single turn pattern, especially if the pattern is low and tight (like say after a "low pass").

I also prefer a fast pattern, slowing down once on final - but again that is glider-specific.

And of course, ALWAYS adjust for your actual altitude/energy state and do what is needed to land safely!

Bottom line, I think it helps to get everything set on downwind (gear, flaps, initial spoiler setting, airspeed) then concentrate on flying a safe pattern. To me, messing with flaps and spoilers while making base and final turns and changing aircraft configuration throughout the pattern is asking for trouble (see all the ASW-20s that crashed early on with the gear cycling on final, ex-Libelle pilots thinking they were pulling the spoilers!)

Finally - I detest big, high, long final patterns. Why? The longer the pattern, the more chance something can get messed up. 1000' on downwind is absurd! Get in tight at 600' or so, two (or one) tight turns to final, land.

Because when you start landing out, at 1000' you should still be trying to thermal away (with a field picked out), and when you do have to set up your pattern, you will be low and close - so you can see what you are getting into!

Kirk
66

On Tuesday, June 2, 2015 at 1:24:53 PM UTC-4, kirk.stant wrote:

Bottom line, I think it helps to get everything set on downwind (gear, flaps, initial spoiler setting, airspeed) then concentrate on flying a safe pattern. To me, messing with flaps and spoilers while making base and final turns and changing aircraft configuration throughout the pattern is asking for trouble (see all the ASW-20s that crashed early on with the gear cycling on final, ex-Libelle pilots thinking they were pulling the spoilers!)

What helps even more is starting with the POH before developing your own type specific procedures :-).

For instance: Landing flaps in the 20 are reserved for final approach, per the POH, for a whole bunch of very good reasons.

-Evan Ludeman / T8

On Tuesday, June 2, 2015 at 1:37:48 PM UTC-5, Tango Eight wrote:
On Tuesday, June 2, 2015 at 1:24:53 PM UTC-4, kirk.stant wrote:

Bottom line, I think it helps to get everything set on downwind (gear, flaps, initial spoiler setting, airspeed) then concentrate on flying a safe pattern. To me, messing with flaps and spoilers while making base and final turns and changing aircraft configuration throughout the pattern is asking for trouble (see all the ASW-20s that crashed early on with the gear cycling on final, ex-Libelle pilots thinking they were pulling the spoilers!)

What helps even more is starting with the POH before developing your own type specific procedures :-).

For instance: Landing flaps in the 20 are reserved for final approach, per the POH, for a whole bunch of very good reasons.

-Evan Ludeman / T8

Obviously, type-specific procedures specified in the POH take precedence. In the case of the LS6, it pretty much just says "for landing, put flaps in L". Having flown the 20, I totally agree with the POH procedure!

My point is that it's possible to make a landing pattern procedure so complicated that the pilot's attention is distracted "by doing everything in the right sequence at the right time" - forgetting that the most important thing is to arrive on short final at a suitable airspeed and height, and at the desired location!

Kirk
66

On Tuesday, June 2, 2015 at 12:37:48 PM UTC-6, Tango Eight wrote:
What helps even more is starting with the POH before developing your own type specific procedures :-).

-Evan Ludeman / T8

Great comment!

We have a generation of pilots that has never seen (or forgotten) the folks that died learning what not to do.

I was taught that there is nothing inherently dangerous in using spoilers in the circuit, provided that the correct speeds are maintained.

With spoilers out, even just cracked open, during base and finals turns safe speed margins are reduced, i.e. inside wing flying slower, reduced lift from deployed spoilers and wind shear (again inside wing flying slower).

However, I was advised NEVER to use them on the base and finals turns (unless absolutely necessary and me paying full attention) and here is why:

Imagine that you normally use spoilers during these turns, with no problems at all, but one day you are returning from a 9 hour cross country flight, it’s been a long final glide and energy is low. Also the weather has changed and the wind is gusting from an approaching storm front.

So you are fatigued, the glider is in a low energy state and wind is gusting. The holes in the cheese line up and you crack the spoilers during a steep base turn with speed too low. The end.

I haven't read every comment in this thread from the beginning, so maybe someone has observed this previously. If so, apologies for the repetition.

There's nothing inherent about turning that will cause a stall or spin. There's nothing inherent about deploying the spoilers that will cause a stall or spin. There's noting inherent about putting out the landing flaps that will cause a stall or spin. There's noting inherent about turning low that will cause a stall or spin. There's nothing inherent about doing them all at once that will cause a stall or spin. But, the more moving parts there are in your approach maneuvers the more attention it will take to keep everything in proper order. A few examples:

Turning below a few hundred feet presents the pilot with a very different peripheral scene because the inside wing tip traces a circle against the ground that is in the direction of travel rather than the opposite direction at higher altitudes. This tends to make it feel as though you are slipping and over-ruddering the turn can become a risk. Not a problem if you fly the airplane properly.

When you deploy the spoilers two things happen. First, you spoil the lift on the portion of the wing spanned by the spoiler (that's why they're called spoilers). This means to maintain unaccelerated flight the rest of the wing needs to produce more lift, which the pilot may compensate for by increasing angle of attack. Not a problem if you fly the airplane properly, but if you are too close to the angle of attack for stall, you can end up on the wrong side of the Cl vs alpha curve.

Second, deploying spoilers increases drag so the descent angle needs to increase to keep from bleeding off airspeed. The net effect between loss of lift and increase in drag depends a bit on the glider and the airspeed and g-load, but suffice to say that airspeed and AOA will have additional influences inflicted on them. Not a problem if you fly the airplane properly, but a bunch of rates and angles are going to change when you tug on the spoiler of flap handle.

I, for one, try not to change too many things too quickly all at once in the pattern, or if I do, I tend to push the nose over a bit in case I get distracted by, you know, looking out the window. Can you yank aggressively on all the handles at once and not create a problem? Absolutely, but it helps to pay good attention if you do.

The FAA preaches stabilized approach for a reason:

https://www.faa.gov/news/safety_brie...opic_16-11.pdf

Andy Blackburn
9B

On Saturday, January 6, 2018 at 1:38:02 AM UTC-7, Andy Blackburn wrote:
....
Second, deploying spoilers increases drag so the descent angle needs to increase to keep from bleeding off airspeed. The net effect between loss of lift and increase in drag depends a bit on the glider and the airspeed and g-load, but suffice to say that airspeed and AOA will have additional influences inflicted on them. Not a problem if you fly the airplane properly, but a bunch of rates and angles are going to change when you tug on the spoiler of flap handle.
....
Andy Blackburn
9B

This, I believe is the key that people are not considering. The physics of it is such that when the air brakes/spoilers are deployed, they disrupt not only the lift, but increase the drag. As such, if you kept the aircraft in the same attitude, you would increase the AOA and are more likely to stall.

However, if you maintain your airspeed, to do this and deploy the spoilers, you would need to change the attitude of the aircraft into a more nose-down position. This would decrease the AOA, thus compensating for the decreased lift and increased drag, and the net effect would be no significant change to the stall speed, whether you are turning or flying level wings. The AOA remains the same, and IAS and stall speed also remain the same.