Effect of a helicopter behind you?
 

Hello! After trying 2 get a PPL (A) 2 years ago and getting interrupted by life I'm back in the cockpit and determined to get it this time... I have a question: What effect can/does a helicopter behind you when in a circuit have?

This site talks about the effect of a hovering chopper, and a chopper that is ahead of you and moving forward. But I can't find anything on a chopper coming in behind you. Thanks.

Um, none. Zero.

A non effect would be that no matter how slowly you fly your circuit, the helicopter pilot can fly slower yet!

Thanks both.

The afternoon rain never gets you wet in the morning.

There's just one real effect: You get nervous.

Apart from that, you need to understand that helicopters have different operating patterns and requirements. I'm not a helicopter pilot, but I know that although they can hover, they prefer not to do so. At least, not a few hundred feet of the ground. If their engine stops, they need altitude to first set up an autorotation, and then use the rotor energy to cushion their landing. So hovering a few feet above the ground is ok, and hovering maybe 500+ feet is also OK, but anything in between can be a problem. Furthermore, they can fly their circuit differently, and don't necessarily have to aim for the runway. It's perfectly OK for them to aim their final approach to a parallel grass area, and from there hover-taxi to the ramp. So they might just turn to base and final inside of you, and "land" parallel to you. And, of course, they produce quite a bit of wind when hover-taxiing, so you might want to hold on to the controls if they're doing it near you.

If you operate from a field that is also frequently served by helicopters, why not invite one of them over for a coffee and voice your concerns/ignorance. They'll be able to give you a lot of advice.

A helicopter produces downwash equal to its weight. If you fly through it, it can have disasterous effects on a light aircraft, so treat it with respect. If the helicopter is behind you, it is unlikely to have any effect, but if its ahead or has crossed your path you need to allow sufficient time for the wash to sink. A colleague of mine was killed after a large helicopter flew over the runway he was landing on when his aircraft rolled in the downwash.

You're unlikely to find a helicopter behind you in a circuit: they are supposed to avoid the flow of fixed wing traffic.

BackPacker, to correct your assertion that helicopters need >500ft to autorotate we can autorotate from the hover all the way to the moon. Almost ;)

It is a matter of energy management from three sources: height, airspeed and rotor RPM (RRPM). The ideal is to arrive with zero airspeed at 5-10ft agl then sacrifice the RRPM to cushion the touchdown.

To the OP, a helicopter behind you in the circuit should have no effect whatsoever. Should you follow or cross a helicopter flight path then be aware of the tip vortices which can produce a noticeable bit of 'wake turbulence', but this is all dependent on the size and speed of the helicopter along with the size of the aircraft.

Whopity, where and when was the fatality that you refer to please?

Well, seeing as we've already drifted the thread, two things:

Yes, helicopters have an "avoid zone" of airspeed vs altitude for a safe gliding return for a landing. Fixed wing planes have an avoid zone too, it's just not published, and not taught. For helicopter pilots it's prime information during training, and in flight manuals. Ask yourself, like a helicopter, if you were flying your Cessna at 100 AGL, and 50 MPH could you enter a glide after a sudden engine failure, and accelerate to glide speed so as to be able to flare for a safe landing - before you hit the ground? No, a fixed wing plane won't do it either, just no one tells you, 'cause you're probably no supposed to be flying there. Sometimes helicopters have to, so it's published and trained.

And, yes, helicopters produce wake turbulence. It does change shape from the hover to cruise flight, though it's going to have the same negative effects on airplanes who might blunder into it, as would be the case of the airplane flying into the wake of another airplane.

Helicopter pilots may be given more direct traffic patterns, but be confident that ATC, and the helicopter pilot themselves are well aware of the burden of traffic avoidance (and the helicopter pilot has the better view!).

Helicopters have surprising similarities to airplanes in ways you would not expect.

I was on final for the hard runway in a Cessna 150 when I was overtaken by a Squirrel going for the Northside grass. It seems from above that I had a lucky escape with just having a massive wing drop. I went around. I then had a 'conversation' with the 'lady' in the Tower who intimated that making it official would be very complicated for me. I then had to rush off to work. Later, I got a very friendly phone call from the Squirrel pilot and we had a nice chat and he agreed that whilst he wasn't going for the same runway as me, overtaking me had consequences he hadn't appreciated. I guess that Tower person had mentioned it to him!

BackPacker's comment is a good one - it's good to talk.
TOO

Of course it works the other way as well. I know of a case when was in Germany when a German F104 (Starfighter) decided to phase a German Army CH53 by a close pass over the top.......
The rotor disk folded upward in chaos , with the inevitable 100% casualty result.

Of course, in exceptional circumstances a strong tailwind could carry a helicopter's downwash forward and under a preceding fixed wing on approach. The fixed wing could descend into the resulting turbulent air pocket and suffer a very hard landing.

I'd be interested to see a mathematical explanation of that phenomenon.

It's a bit contrived to discuss downwind approaches, isn't it? In practice you'd have a similar effect to a helicopter in front of the fixed wing during an into-wind approach - but that's not really the question asked.

Minor point, but that sad occasion was St Mawgan rather than Culdrose.

Yeah, you might want to rethink that one. A helicopter might be able to fly with -ve airspeed but I'm pretty sure an airplane can't!

The lack of understanding about fundamental POF displayed by some here is a little scary!

Please, take a moment to analyse things.

Actually, the entire thread is ridiculous! (Sorry, but it is)

Just a daft response in the spirit of the original question.

"The lack of understanding about fundamental POF displayed by some here is a little scary!

Please, take a moment to analyse things.

Actually, the entire thread is ridiculous! (Sorry, but it is)
Agreed Sam.
Perhaps some might have been more aware about avoiding their effect on a helicopter in front of them ( Particularly one parked on the ground?)

Hat ,Coat etc .........