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Aborted takeoff in Glider

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Aborted takeoff in Glider

Old 13th Oct 2017, 00:55
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Firstly, I hope the poor chap makes a speedy recovery.

About 29 years ago I did a gliding course at Sealand. I may have convinced myself of this having mulled this over on more than one evening but....

Doesn't the disturbed airflow as a result of the brakes being open make a dramatic contrast in wind noise? I'm sure I recall it making a din.

If this is the case, wouldn't a pilot recognise this sound?

As I said, it was a long long time ago now.
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Old 13th Oct 2017, 08:02
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Originally Posted by the_flying_cop View Post
About 29 years ago I did a gliding course at Sealand...but...

Doesn't the disturbed airflow as a result of the brakes being open make a dramatic contrast in wind noise? I'm sure I recall it making a din.

If this is the case, wouldn't a pilot recognise this sound?
Winch launch or tug? Just speculating but I'd guess that engine/prop noise from the tug at full throttle might mask this. Plus I'd guess it'd become more apparent as the launch developed, by which time the pilot would have been really busy. I believe aural processing is the first to go when things get critical.

Very unfortunate he missed the handle moving aft but it happened so very quickly when I'm sure his focus was out and ahead.

Speedy recovery.
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Old 13th Oct 2017, 11:58
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There is another aspect of this not discussed
What would have happened if he HAD suddenly realised and slam closed the brakes?

I suspect that the glider would have soared upwards - thereby bringing the other great danger of aerotows into focus - that of dragging the tow plane tail up leading to a nose dive crash into the ground.
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Old 13th Oct 2017, 14:06
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Most airbrakes produce very little change in trim, especially on an aerotow. Closing them would almost certainly have restored instaneously normal climb performance.

I have also witnessed countless departures with airbrakes open. The problem is most people or totally unaware they have a problem or if they are that their airbrakes might be the cause. I’ve seen a perfectly good glider winch launched and crash offsite because they brakes were open. Glider pilots are generally not taught to trouble shoot and emergency training normal consists of cable breaks and stall/spin awareness and recovery.

PM
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Old 13th Oct 2017, 16:48
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dsc810,

I think the pilot would have been prepared for any sudden position change, following the closing of the brakes. However, my comment is not meant to minimize the risk of a tow-plane upset. When I'm towing, below 300', my fingers are poised on the release handle.

I used to instruct in and tow Blaniks. The airbrakes would always come open during takeoff if they weren't locked. Once I was towing an inexperienced pilot in a non-radio Blanik and the airbrakes came open during the takeoff roll. I was climbing at less than 200' per minute.

I was reluctant to give the rudder-waggle signal for "airbrakes open", because the roll secondary-effect could be mistaken for the "release now" signal.

So my plan A was to try to turn and climb to a suitable release location in the circuit, which I was able to do. Plan B was to continue straight ahead and release him over a nearby airport.

Taking to the pilot afterwards was very illuminating. Until he released, he had no idea that the airbrakes were open and he assumed that the low rate of climb was due to engine problems. He told me that his hand was on the release, anticipating a signal from me!

Talking to another tow pilot about my experience, he told me of a similar experience, where he had given the "airbrakes open" signal, which the glider pilot mis-interpreted, released, got too slow and spun-in.

I decided that I would never use the rudder-waggle signal unless in absolutely dire straits. Of course these days, we have radio, so the problem has gone away. However, we still teach all the signals and the way to minimize mistakes, is to do a very quick rudder-doublet.
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Old 13th Oct 2017, 18:12
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Hello India 42!

Nice to hear from another tuggie!

I know they must do things differently in California! We certainly agree that no signal is better than one the glider on tow will probably misinterpret! And over here in the UK asking the tuggie to waggle the rudder at low level is not a good idea at all at all.

As for communicating with radio, that is asking a lot from an early solo glider pilot who is rather busy dealing with the airtow. Keep it simple! Just drag him up! (unless he gets too high behind you, in which case he will be faced with the problem of finding which field, schoolyard, or parking lot is now decorated with a nice blue 180 foot rope with rings at each end.

Early in my career at Booker, instructing in a glider, when we got out of position both the tug and I let go at the same moment. I had to go look for the rope later, on the ground. Thought it would be easy to find again......
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Old 13th Oct 2017, 18:29
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Of course these days, we have radio

Which isn't always on, and sometimes (as happened to me) I had turned it down because of a lot of chit-chat.
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Old 14th Oct 2017, 08:42
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Finding yourself in any aircraft at low level with no power and your only option is to choose the least painful place to crash is not nice, so training is designed to reduce the risk as much as possible. Pretty much in gliding the check list is standardised.
C Controls full and free
B Ballast within limits
S Seatbelts on and tight
I Instruments. All OK
F Flaps set for TO
T Trim set for TO
C Canopy closed and locked
B Airbrakes close and locked
E Eventuallities, what are you going to do something goes wrong

Additionally for the wing man to shout
Rope on and secure
Brakes closed and locked

Training has reduced accidents substantially in recent years, dont let standards slip.
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Old 14th Oct 2017, 09:03
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mary,

I wish I was in California! I'm in Calgary, where winter is beginning. However, it's also wave season and we had a two-seater reach FL325 a week ago!

My club has been using radio routinely for the last twenty years and we have found that by the time a student is ready to solo, that using the radio is not an issue.
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Old 15th Oct 2017, 15:12
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Brakes opening on tow is not a major safety issue. What can become a major safety issue is the tow being continued with brakes open because the pilot was simply unaware they were open. That cannot happen if the airbrake handle is guarded (hand on, or immediately behind, the handle).

Use of airbrake was my preferred method of managing slack rope on aerotow in the ASW19b or ASW28. There is no trim change or other upset when the brakes are opened only an increase in drag. Since I use brakes for takeoff (improved low speed roll control), and for slack rope management, my left hand is usually on the brake handle for the entire tow. Those who know these gliders will know that a hand on the closed airbrake handle is also very close to the release.

I've spent a bit of time at the front of the rope too. Citabria, Scout, Pawnee, and 180 Super Cub in USA and Citabria in UK. I never had to dump anyone or wave anyone off but a Standard Cirrus pilot who pulled up aggressively and turned away without releasing the rope got my attention once! The Cirrus back released about the time I was starting to pitch down. We had a discussion when he landed. He said he had pulled the release and was not aware that the rope had no released. The discussion continued!
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Old 1st Nov 2017, 19:37
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Originally Posted by Deltasierra010 View Post
Pretty much in gliding the check list is standardised.
C Controls full and free
B Ballast within limits
S Seatbelts on and tight
I Instruments. All OK
F Flaps set for TO
T Trim set for TO
C Canopy closed and locked
B Airbrakes close and locked
E Eventuallities, what are you going to do something goes wrong
Although I'm sure there's good reason behind that order I do wonder why the more conspicuous canopy check appears before airbrakes?

To my mind, this order seems a little more fool proof;
...
B Airbrakes close and locked
C Canopy closed and locked
E Eventuallities, what are you going to do something goes wrong
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Old 2nd Nov 2017, 07:23
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Originally Posted by dynamics View Post
Although I'm sure there's good reason behind that order I do wonder why the more conspicuous canopy check appears before airbrakes?

To my mind, this order seems a little more fool proof;
...
B Airbrakes close and locked
C Canopy closed and locked
E Eventuallities, what are you going to do something goes wrong
I sometimes do E before C so BEC. The reason is misting inside the canopy, which clears as soon as there's an airflow through it. I've occasionally asked the wing man to hook me on, go to the wingtip, wait until I've shut the canopy and start signally. Sometimes I have to do as best I can to hold my breath until the glider is moving, but I emphasis once it is, the misting clears PDQ.

If he signals before I'm ready I can drop the cable.
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Old 2nd Nov 2017, 10:12
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It's many decades since I flew a glider, evidenced by the fact that my ab initio instructor at Lasham was Derek Piggott, but I do recall "brakes in and locked" as an essentiial check.

I've come in though, only to go back a little way in the thread to a post which said:

I always started aerotow takeoff roll with airbrakes open and closed them when I have good roll control.
and ask; "Why?", out of sheer curiosity.
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Old 2nd Nov 2017, 13:56
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Again some years since I have flown gliders. Can someone say where in the CBSIFTCBE pre-flight checks is C for Cable attached ?


I also thought you needed to do three cable checks.. Free Drop, Back Release, and Release under Tension. (where the cable guy pulls on the cable, you release and he ends up flat on his back.!)
.
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Old 2nd Nov 2017, 18:17
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Originally Posted by old,not bold View Post
It's many decades since I flew a glider, evidenced by the fact that my ab initio instructor at Lasham was Derek Piggott, but I do recall "brakes in and locked" as an essentiial check.

I've come in though, only to go back a little way in the thread to a post which said:
I always started aerotow takeoff roll with airbrakes open and closed them when I have good roll control.
and ask; "Why?", out of sheer curiosity.
Some gliders have very poor roll control at low speeds, and an aerotow takes time to accelerate to where it's adequate. A winch launch OTOH... But in this case it's deliberate, the pilot know what they were doing and why, and would have had the airbrake lever in their hand. of course that means they didn't have a hand to devote to the release knob...
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Old 2nd Nov 2017, 19:49
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Originally Posted by scifi View Post
Again some years since I have flown gliders. Can someone say where in the CBSIFTCBE pre-flight checks is C for Cable attached ?
I also thought you needed to do three cable checks.. Free Drop, Back Release, and Release under Tension. (where the cable guy pulls on the cable, you release and he ends up flat on his back.!)
.
The release checks you mention are now done as part of the daily inspection, along with positive control checks.
So the cockpit C- controls check is now just fully round the box all controls free and full movement.
The cable goes on after you have done the full CBSIFTCBE routine.
I always confirm to the cable handling man "brakes closed and locked cable on please"

Personally I miss out the E bit ('cos I learnt before it was added) which drives instructors mad but I add in D to make sure tail dolly is off, and a U to make sure the undercarriage retract lever is in its fully locked down detent position.
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Old 3rd Nov 2017, 00:50
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Some gliders have very poor roll control at low speeds, and an aerotow takes time to accelerate to where it's adequate.
Yes, I see that, but in what way do the airbrakes help with low speed roll control? I would have imagined that, if anything, the additional drag would contribute to the slow acceleration, but maybe I'm being dim......

Afterthought.......perhaps gliders now have differential airbrakes/lift dumpers that would provide some roll control, and I'm just 30 years behind the curve.....?
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Old 3rd Nov 2017, 01:11
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Well, ONB, the drag issue is not relevant at the low speeds at the start of an aerotow ground roll (drag proportional to the square of the speed and all that). But as to your more relevant point, some argue that having the brakes deployed at low speed diverts more airflow over the inboard section of the ailerons and hence give them more bite more quickly. Looking at the schematic of the ASW19/20 series (whose pilots frequently adopt this method) shows that there just might be something in this.
But none of that is relevant to the subject of the original post. The guy had a bad day and ran out of luck. He's known to me and is not a dork - there but for the grace of god and all that....
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Old 3rd Nov 2017, 19:26
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Originally Posted by EXDAC View Post
Brakes opening on tow is not a major safety issue. What can become a major safety issue is the tow being continued with brakes open because the pilot was simply unaware they were open. That cannot happen if the airbrake handle is guarded (hand on, or immediately behind, the handle).

Use of airbrake was my preferred method of managing slack rope on aerotow in the ASW19b or ASW28. There is no trim change or other upset when the brakes are opened only an increase in drag. Since I use brakes for takeoff (improved low speed roll control), and for slack rope management, my left hand is usually on the brake handle for the entire tow. Those who know these gliders will know that a hand on the closed airbrake handle is also very close to the release.

I've spent a bit of time at the front of the rope too. Citabria, Scout, Pawnee, and 180 Super Cub in USA and Citabria in UK. I never had to dump anyone or wave anyone off but a Standard Cirrus pilot who pulled up aggressively and turned away without releasing the rope got my attention once! The Cirrus back released about the time I was starting to pitch down. We had a discussion when he landed. He said he had pulled the release and was not aware that the rope had no released. The discussion continued!
There may be a case for Airbrakes on the TO roll but to be honest I have never seen it used, nor has anyone mentioned using them to take up cable slack, it certainly is not taught by instructors. My own way of avoiding cable slack is, when the tug turns make sure to stay on the outside of the turn
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Old 4th Nov 2017, 16:31
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Originally Posted by Deltasierra010 View Post
There may be a case for Airbrakes on the TO roll but to be honest I have never seen it used, nor has anyone mentioned using them to take up cable slack
Using wheel brake to prevent jerking forward and possibly over-running the rope is a useful technique especially when launching on a down slope. With a glider such as the ASW20 where wheel brake is engaged by fully opening the air brake, the glider will be seen to start the initial take-off roll with air brakes fully open - but closed and locked as soon as the combination is properly under way.
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