sticky wicket
 

Folks,
Finding myself in a sticky wicket. need some help /advice on something.
I need to prove to a court "when a helicopter is in a hover" in terms of what speed below which a helicopter is considered to be in a hover. We all know that when it looses translational lift (around 25kts) it is considered to be hovering I just need this in writing from an approved source and struggling to find this. . If any one could point me in the direction of some approved training notes or other that spells this out that would be great. .

here's some Federal advice for the minute...the rest of the tribe will be along shortly !

Aeronautical Information Manual (AIM) - Page 204

heading.https://www.faa.gov/regulations_poli...a/hfh_ch09.pdf

AC 27.49. § 27.49 (Former § 27.73) (Amendment 27-44) Performance at Minimum Operating Speed. (For § 27.73 prior to Amendment 27-44, see AC 27.73) a. Explanation. Amendment 27-44 adds a requirement to determine out-of-groundeffect (OGE) hover performance. Once reserved for special missions, OGE operations are now a common practice.

(1) The word "hover" applies to a helicopter that is airborne at a given altitude over a fixed geographical point regardless of wind. Pure hover is accomplished only in still air. For the purpose of this manual, the word "hover" will mean pure hover.
https://www.faa.gov/documentLibrary/...thru_Chg_6.pdf

You can be in a hover with far more than 25 kts of wind. - what have you done wrong toohigh?

Surely the court can accept dictionary definitions of hover - it's not rocket science - it's what a Kestrel does when hunting, it's what a waiter does when waiting for a tip - if it's not stationary, it's not a hover.

I am not sure we would all agree

If I was stationary over a helideck with 50kts of wind, I would certainly consider myself to be hovering, and would definitely have translational lift.

If I was (inadvisedly) flying a downwind approach with a 40kt tailwind, at the point where I lost translational lift, I would not expect to be in anything resembling a hover.

Could also be a matter of terminology
To me a hover is stationary over one spot
If I am moving at all , or maneuvering to a helipad it is a hover- taxi

Without more specific context of the scenario, you may struggle to find the appropriate "approved" source material. For example, in one acceptable FAA source the term "hover" is used in various scenarios.
https://www.faa.gov/regulations_poli...a/hfh_ch09.pdf

But when discussing a hover from a performance standpoint, OGE and IGE take you in a different direction.

spot on I’d say. CAP413 (UK R/T phraseology) has this to say which I think wraps it up nicely:

HOVER’ describes a manoeuvre where the helicopter holds position whilst airborne in ground effect, waiting to proceed. Hover allows spot/ axial turns (i.e. about the central axis of the helicopter). When required, further instructions should subsequently be transmitted to permit the helicopter to proceed.

The term ‘AIRTAXI’ shall be used when it is necessary for a helicopter to proceed at a slow speed above the surface, normally below 20 knots and in ground effect (ICAO).

A perfect example, as happily witnessed several kestrels doing whilst I was playing golf today - they coped admirably with a good 25 knots of wind much better than I did! On a much larger scale, submarines also establish a pure hover prior to launching missiles.

Jack

thanks for all your posts
I am being accused of being "un safe" for bringing the speed back to 40kts indicated during an air test.(no passengers on board very low weight)
we were out of the dead mans curve and above minimum safety speed for single engine flight . we had a 30kt head wind so the ground speed was 10kts.... the word hover has been thrown to the investigation and has had the effect to implicate that somehow the
manoeuvre was un safe. within the context of a factual investigation this use of the word is nothing more than inflammatory and a low punch. I was attempting to try and show that OK whilst we were slow " effectively nearly in a hover". we did also have forward airspeed on so precisely what was unsafe about it mr investigator.

Thanks for the above definitions: " a hover is when the aircraft is Geostationary" at a constant altitude"
as we had 10kts of ground speed we weren't actually in a hover. so whichever way you look at it the word should not be in the report.

Yup, heli flying terrifies everybody except the drivers

Yes toohigh13. Fight is with all you can.

But pray tell us, what is an „air test“?

It all sounds very curious! By 'air test' I guess you mean a maintenance check flight? You refer to 'we' but with no pax, so presumably accompanied by another pilot as crew (it's obviously a twin engined aircraft) - was it they that reported you, or somebody on the ground, or did the flight not end well and the AAIB get involved? 'Mr investigator' sounds more like AAIB than police. Are the 40 KIAS and 10 kts g/s recorded data, or pilot observation? What does "minimum safe speed for single engine flight" mean - it has no regulatory definition. If you are trying to prove a factual statement, to refute a claim, you should relate the IAS to an RFM performance standard - Vtoss, Vy, OEI HOGE etc.

I don't expect answers, but these are the kind of thoughts that jump to mind when reading the account.

Exactly, 212. One additional thought re the translational lift term ( which adds to your point ). That term relates to the drop in power required for level flight as one translates forward from hover to some forward speed. The shape of that power required plot is a bit different for each different rotor/aircraft model. If one then looks at the shape of that plot, saying that one speed is the translational lift speed is an argumentative point-its a curve. Thus-your last sentence is the point and melds the technical and legal aspects.

Wonder what these chaps are doing if not hovering? Ground effect? CAP needs a little rework if that's all it has to say I feel, certainly doesn't wrap it up nicely.

Yep, fair point. From his original post, I assumed the incident was in an airfield or low ground environment. The only bit that really needs to go in the definition is the mention of ground effect.

And back to the original point. There is absolutely no problem if a helicopter is brought to a hover, whether a free air hover (air-referenced) or a geostationary hover (ground- referenced) provided;

A. Your downwash isn't causing an issue

B. You have the performance AEO and capability to safely stay airborne or safely land following eng failure (eg you are not sat in an avoid curve if it exists at that weight)

C. You are not exceeding any published limit.

I suspect you have been given an draft of some report to review as the subject before it's published. Definitely worth pushing back on it. If you're not getting traction, then elevate it through the organisations chain of command.

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I’m curious, how did those accusing you expect you undertake the maintenance check flight if the aircraft was too unsafe to hover? We’re you restricted to a running takeoff and running landing? 😂 God forbid you flew one of those dangerous vertical CAT A departures.

Who is doing the accusing - Employer? Regulator? Third party?

I'm guessing either you're being prosecuted, or you've been sacked and are taking an employer to court?

Helicopters do things that are 'unsafe' every day, but that doesn't make it illegal, and by the sound of it you weren't even that unsafe, 40kts gets you out of a lot of holes.

Pure speculation on my part but looking at the location of the OP i'm wondering if someone from one of the offshore operators got pinged by the HOMP / FDM police for doing something that did not follow the magenta line and is now the subject of an internal disciplinary?