Helicopter takeoff
Discussion
I just watched a quick video of the AAC Apache's on facebook, and saw the Apache take off using a rolling approach. I seem to remember either in Chickenhawk or one about the RN's Lynx helicopters in the Middle East that rolling take-offs were required when heavily laden. I may be wrong, but the Apache didn't look desperately bogged down, but just seemed to be doing it as a matter of course.
Where possible, is it just easier for a helicopter if it has an undercarriage to do this (i.e. increase the speed over/under the 'wing' as with an aeroplane), or is there another reason?
Where possible, is it just easier for a helicopter if it has an undercarriage to do this (i.e. increase the speed over/under the 'wing' as with an aeroplane), or is there another reason?
I wonder if the threats to it are a consideration, I'd imagine a helicopter going straight up then pitching forward to move off would be a good standing target. Whereas if they go shooting down the runway before getting any altitude their a rapidly moving target.
Just my thoughts with no fact included!
Just my thoughts with no fact included!
Is it not standard practice if you have the room to take a run up you di it as it's easier to get airbourne. My office has a view of Aberdeen Int Airport and the Helicopters here do the same thing.
From my time in the RAF Merlins, Puma's and seakigs all did the same. Harriers could do a vertical take off but rarely did.
From my time in the RAF Merlins, Puma's and seakigs all did the same. Harriers could do a vertical take off but rarely did.
muppetdave said:
Yeah very true and I think I did read that in one book. My suspicion is it's still predominantly to do with improved lift, but am not a flier.
It does increase the amount of lift and as far as I am aware (also a non-flyer) there aren't really any downsides apart from the space it takes up. If you've got the room then why wouldn't you?Prawo Jazdy said:
Power required vs. airspeed makes a U-shaped curve when plotted. So, with a small forward velocity you'll travel down the left hand side of the curve a little and use less power to get airborne. That's how it looks, but I can't remember why...
Once you start moving forward the rotors are in clean air, rather than the turbulent stuff left behind by the last rotation. That's AFAIK anyway...Prawo Jazdy said:
Power required vs. airspeed makes a U-shaped curve when plotted. So, with a small forward velocity you'll travel down the left hand side of the curve a little and use less power to get airborne. That's how it looks, but I can't remember why...
Translational lift. It's when the rotor system becomes more efficient as you move away from ground effect while hovering to the cleaner air in front of you as you move into it.rhinochopig said:
Unlikely to be chickenhawk. A rolling take-off is difficult with skids and an lz only a couple of rotor discs wide.
It was Chickenhawk. Don't have my copy handy right now, but the technique was mentioned a few times - each time they had sufficient power to lift off a few feet, just not enough to then continue lifting up out of the ground effect (or something like that - been a while since I last read it and I'm a bit hazy on the details now). So they could get the skids off the ground, then start flying forwards at low level until they reached the point as note above where the power required to continue lifting drops off. I also seem to recall reference to doing this technique by flying a curved path, so that the tail rotor was using slightly less power allowing more to be given to the main rotor.Edited by rhinochopig on Thursday 27th November 17:46
I used to fly Merin and Puma (both wheeled helicopters) and we practised running take offs for scenarios when we were power limited; as others have said it uses less power than a hover takeoff, especially hot and high. I doubt there's any tactical considerations as runways tend to be well protected anyway! When we use to go to overload capacity on the Merlin we had to do a running takeoff to minimise strain on the gearbox/drive train. It may be they were just heavy......or even just did it for the hell of it 
twister said:
rhinochopig said:
Unlikely to be chickenhawk. A rolling take-off is difficult with skids and an lz only a couple of rotor discs wide.
It was Chickenhawk. Don't have my copy handy right now, but the technique was mentioned a few times - each time they had sufficient power to lift off a few feet, just not enough to then continue lifting up out of the ground effect (or something like that - been a while since I last read it and I'm a bit hazy on the details now). So they could get the skids off the ground, then start flying forwards at low level until they reached the point as note above where the power required to continue lifting drops off. I also seem to recall reference to doing this technique by flying a curved path, so that the tail rotor was using slightly less power allowing more to be given to the main rotor.Edited by rhinochopig on Thursday 27th November 17:46
)When I used to fly offshore alot it was always common practice to build up speed along the runway then lift off. On the rigs for obvious reasnos it was always verticle.
Agree with previosu comments about the power requirements etc. The chopper used to shake like a good un on verticle lifts!
Agree with previosu comments about the power requirements etc. The chopper used to shake like a good un on verticle lifts!
Burrow01 said:
twister said:
rhinochopig said:
Unlikely to be chickenhawk. A rolling take-off is difficult with skids and an lz only a couple of rotor discs wide.
It was Chickenhawk. Don't have my copy handy right now, but the technique was mentioned a few times - each time they had sufficient power to lift off a few feet, just not enough to then continue lifting up out of the ground effect (or something like that - been a while since I last read it and I'm a bit hazy on the details now). So they could get the skids off the ground, then start flying forwards at low level until they reached the point as note above where the power required to continue lifting drops off. I also seem to recall reference to doing this technique by flying a curved path, so that the tail rotor was using slightly less power allowing more to be given to the main rotor.Edited by rhinochopig on Thursday 27th November 17:46
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