Twin Otter Flaps

[bushy127]

HI,

Could some explain how this system works and is it a hydraulic system.

THanks

[liklikrokrok]

Hydraulic yes..how it works ??hmmm...increases wing surface area and camber to generate required lift at lower IAS

LLRR

[411A]

Full span, although not equal, IE: the ailerons extend some, but not as much as the flaps.

Standard hydraulic actuators, not operated by jackscrews.

1500 PSI hydraulic pressure (I think, been a very long time since I flew 'em...and yes, at that time, no restriction on the use of beta or reverse in the air, which there is now).

If one was very proficient, a 145 knot approach could be flown to 1/2 mile final, prop controls forward, select a slight amount of beta, slow very quickly, extend 10 flaps, land, and turn off in 2000 feet.

Need to land shorter?
Start slowing just a tad sooner, and use more flaps.

deHavilland demo pilots demonstrated....
Cross the threshold at 1000agl, with forty flaps and a very low speed, select just a tad of beta, descend like an express elevator, exit beta just before touchdown, land and turn off the runway in 1000 feet.

Howsomever, foul it up and the chief pilot would not be pleased.

[glad rag]

Sorry...

....but what is BETA?

glad rag

[AtoBsafely]

Beta

In Beta range the propeller blade angle is set by the power lever position (ie not constant speed operation). On most setups this is resricted to ground operation such as discing and reverse thrust. If permitted in flight, it can generate a LOT of drag, allowing for amazing STOL approaches.

[barit1]

....but what is BETA?

Here's a DHC-5D pilot demonstrating the use of BETA - and got a bit carried away. (Nonetheless, any landing you can walk away from...)

(I used to have a link to a video of this "arrival" but can't locate it right now)