Difference between Soft-Field and Short-Field Takeoff Technique

[helipaddy]

Hi All,
Im looking for forum thoughts on the different techniques for short field takeoffs and soft field takeoffs. Things to do and things to avoid at all costs!
Cheers
Paddy

[jcarleto]

Avoid bumpy fields. Bumps can cause rotor flap even at near take-off RRPM. Yeah, I know...easier said than done.

*JC*

[ckurz7000]

Hi Paddy, regarding your question about short field and soft field take-offs in a gyro.

Let's start with short field take off. Get your rrpm up as high as possible. I once even used wheel chocks to stop me from starting to skid forward (a helpful bystander yanked them clear of the nose wheel with a long line). Then push the throttle full forward, move the stick back and let rip. As soon as the nose wheel gets off the ground, ease the stick forward to keep the nose wheel just a couple of inches off the surface, not higher. Otherwise the rotor would couse too much drag and you'd waste valuable distance by not getting up to flying speed quickly enough. When the mains lift off, accelerate in ground effect until you reach Vx (that's 95 km/h IAS on my gyro). Pitch up to peg the needle at exactly Vx and keep it there until you cleared the obstacles (if any). After that, pitch to Vy (110 km/h IAS in my gyro) and climb to your cruise altitude.

Some hints that help you eek out every teeny bit of performance:

o) Make sure your tires are well inflated. Low tire pressure increases rolling resistance.

o) If the winds are light and variable, wait for a favorable breeze to blow your way. Every breath of air in your face helps.

o) Get rid of every unnecessary ounce of weight. That includes also excess fuel.

o) Clean the prop and rotor thoroughly. In summer from insects ("parasite" drag) and in winter from any frost or ice accumulation (you should have done that in any case).

o) If you have a ground adjustable prop, pitch it for best climb, which is usually close to max static rpm.

o) If you absolutely must choose between either going slightly uphill or having a bit of a tailwind, usually it's better to take off downhill and deal with the tailwind.

o) Do a thorough magneto and rpm check to ensure you have full power available.

And now to something completely different -- the soft field take off:

I find soft field take offs more tricky in that the rotor handling on the ground is more difficult. On muddy and deep grass strips, I spin up the rotor to about 150 rrpm while still on firm footing. Then I roll to the take off area and onto the runway, accelerating smoothly. The point is not to stop rolling or else the wheels will sink in and you're stuck. Get the nose wheel off as quickly as possible. It will be higher up than in the short field take off, maybe 1.5 feet or so. You will be taking off behind the power curve, therefore you'll have to lower the nose as soon as you are airborne. Accelerate in ground effect to Vy and off you go.

[helipaddy]

Thnks Jon, Ive found the RRPM can take a while to spool up if Im on really rough ground, and it appears that a direct crosswind can increase the ground roll quite a bit too.

Chris, thanks for that. I was interested in the ground roll portion of the two takeoff techniques.
Thanks
Paddy