Drag­ging the winch cable, was the glider still con­trol­lable?

Pilot - - CONTENTS - Words by: Anon

Whilst en­joy­ing my PPL, ex­plor­ing more air­fields and dif­fer­ent air­craft, I also trained as a glid­ing in­struc­tor. I ap­pre­ci­ate many read­ers may have no glid­ing ex­pe­ri­ence−or even break into a cold sweat at the prospect of in­ten­tion­ally fly­ing an air­craft with­out an en­gine−but I found I learned many valu­able les­sons. One in par­tic­u­lar re­minded me of some fun­da­men­tal prin­ci­ples for all my fly­ing.

I was tak­ing a stu­dent for an in­tro­duc­tory flight from a winch launch−the sort where you are pulled up by a metal cable from a ground-based winch. The stu­dent had never flown in a sailplane or light air­craft be­fore and it was a great day for a first flight: CAVOK and calm wind. I had al­ready done a few launches that morn­ing and I started as usual, with my stu­dent in the rear cock­pit and me in the front.

The cable pulls the glider up, ini­tially quite steeply, then the climb rate slows as it reaches the top of the curve−usu­ally around 1,000ft. Af­ter the cable is re­leased, it falls back to the ground us­ing a small drogue para­chute. At the top of the climb, I reached to op­er­ate the cable re­lease tog­gle, which pulls a hook un­der­neath the glider and re­leases the cable from the air­craft. Noth­ing hap­pened. The glider con­tin­ued to fly straight and level. Un­usual, but not a prob­lem as the hook has a safety mech­a­nism and should auto-re­lease if the cable an­gle goes be­yond ninety de­grees to the ground (i.e. the glider over­flies the winch).

Then I got a shock! The glider pitched down vi­o­lently and ac­cel­er­ated to­wards the ground. For a sec­ond I won­dered if I’d had a mas­sive con­trol or struc­tural fail­ure. I con­tin­ued to try the re­lease tog­gle, and shouted for the stu­dent to try his in case mine had failed. Noth­ing seemed to work. I had no con­trol of the air­craft, which was rapidly ap­proach­ing Vne. I was look­ing straight down at the ground, at 800ft. With the ben­e­fit of a para­chute, I had the op­tion of aban­don­ing the air­craft. Hav­ing done a paraglid­ing course a few weeks ear­lier, I could prob­a­bly get out and make it to earth and sur­vive from 800ft, but could the stu­dent, with no para­chute train­ing and only a short safety brief­ing?

But in that split sec­ond the sit­u­a­tion changed. The glider sud­denly lurched up­wards and I had some con­trol again, man­ag­ing to just about get it straight and level. It was a great feel­ing, but short-lived. As the air­speed re­duced, heavy buf­fet started at around twenty knots above the nor­mal cruise speed. I wasn’t sure what was go­ing on: I’d never trained for any­thing like this. I thought that, even though I must now be de­tached from the earth, some­thing was still very wrong… maybe I still had some cable at­tached?

Train­ing kicked in. If I was see­ing stall symp­toms at such a high air­speed in straight and level flight, with no vis­i­ble dam­age to the wing, it had to be due to in­creased weight. I de­duced (cor­rectly as it turned out) that I had hun­dreds of ki­los of steel cable still at­tached to the air­craft, af­ter the (very quick-think­ing) winch­driver had cut the cable at his end.

I quickly got the nose down to keep fly­ing speed and again con­sid­ered if it would be con­trol­lable enough to land. I had con­trol but had to fly a lot faster, and I wouldn’t be able to bank much as that could bring me dan­ger­ously close to the stall speed – and I didn’t even want to think about whether I would be able to re­cover from a stall with the ad­di­tional weight and drag. I tried to bal­ance fly­ing close enough to the air­field to min­imise any ground dam­age from the trail­ing cable, and far enough out to give me a rea­son­able ap­proach.

With things seem­ing un­der con­trol for the first time, I took a sec­ond to think. Was my di­ag­no­sis cor­rect? Could any­one else help? Were there any other op­tions? My fin­ger hov­ered over the PTT. There were other glid­ers about and I was re­ceiv­ing some ground mes­sages on the ra­dio−the sit­u­a­tion was bla­tantly ob­vi­ous from the ground−but I dis­counted do­ing any­thing ex­cept con­cen­trat­ing on the land­ing. Keep­ing con­trol of the glider was the most im­por­tant thing.

Of­fer­ing some un­der­stated re­as­sur­ance to my stu­dent, I put the air­craft down at well above the nor­mal land­ing speed, and was brought to a rapid stop by the drag of the cable. I sat in the si­lence for a sec­ond, be­fore get­ting out to have a look.

Be­hind the air­craft trailed hun­dreds of feet of cable, which I later learned had dam­aged roof tiles and sliced down tele­phone lines. On check­ing the air­craft at­tach­ment, I found it had been fixed in a seem­ingly im­pos­si­ble po­si­tion against the fuse­lage. Now, with­out the ten­sion, and with a slight touch, it fell away to the ground. Con­sid­er­ing the ex­pe­ri­ence, the stu­dent in the back looked sur­pris­ingly calm, but I con­tin­ued to re­as­sure him and we went back to the Con­trol car­a­van for a cup of tea and a bit of a sit-down.

The in­ves­ti­ga­tion found a ground­crew er­ror in at­tach­ing the cable−which should never have been pos­si­ble. This led to an in­cred­i­bly rare sit­u­a­tion, the likes of which even the most ex­pe­ri­enced of glider pi­lots had never wit­nessed. It was only later that the shock hit me of just how se­vere the in­ci­dent could have been, es­pe­cially see­ing the news­pa­per re­ports of the trail­ing cable dam­age.

Now, while this sit­u­a­tion is ob­vi­ously spe­cific to glid­ers, there were gen­eral air­man­ship points I could learn from my ex­pe­ri­ence, to ben­e­fit all my fly­ing.

Firstly, if some­thing can go wrong, it even­tu­ally will – known as ‘Mur­phy’s law’: how­ever un­likely or un­ex­pected, some­thing may hap­pen that you’ve never trained for. Sec­ond, there is a rea­son we learn the the­ory of flight, well be­yond the train­ing nec­es­sary purely for ba­sic op­er­a­tion of the air­craft: a sit­u­a­tion may force you to use this back­ground knowl­edge in a new way. Fi­nally, the old favourite: fly the plane first. In this case, there were very few op­tions open to me any­way, but had I not con­cen­trated on the fly­ing and lost con­trol of the air­craft, the out­come would have been rather dif­fer­ent.

The glider pitched down vi­o­lently and ac­cel­er­ated...

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