The "T-effect"
 

Just been reading an article in R & W about a guy (ret'd Test Pilot) flying his Hiller across States. He says that when he was flying across the open desert, he maintained 15' agl to take advantage of the "T-effect".

I can only imagine that it's similar to fixed wing Ground Effect, because he said that he could maintain speed with less power, or fly at a higher speed using the same power.

I've not heard of rotary Ground Effect having any effect at cruising speeds.

Anybody care to elaborate on the "T-effect"?

Thermal?

OK what's with the 15 word minimum? Jeez guys, between the over-moderating and regulating...

C'mon MG, it's something you probably aren't accustomed to, being a police pilot, and all that.

The "T" effect is when one has drunk too much tea, and needs to be close to the deck so as to land and relieve oneself, old boy:)

Actually TC, old chap, I thought you could have come up with a photo showing the T-effect. :p

Uh-Oh, look up the old thread on Ground Effect here a few months ago. ground effect is available at all speeds to lesser effect above 25 knots or so. In airplanes it has effect up to 150 knots. Some doubt this, because they have an image of a ground cushion built up physically under the aircraft (could you please pass my ground cushion?). Made an interesting thread, never really resolved (meaning nobody ever changed their mind).

search for Autorotation and Ground-Effect and get lost in the 151 replies!

Thanks Nick. I'm fully aware of ground effect in fixed wing, having used it many times in a glider, but wasn't aware that it worked for rotary in the same way. Any idea why he called it the T-effect?

Did he mention at what speed he was flying - as at 15' and 90-100 kts one is not best placed to deal with any malfunction of any kind - even a sneeze or a hiccup could put you into the deck.
Just goes to show that having a brain the size of a planet (he was a TP after all) does not bestow one with a surfeit of common sense.

Lucky he didn't experience the 'W Effect', which occurs when you take out a high tension electricity cable.

ok, we've heard enough about 'P' effect but 'T' or tree effect, is a repelling force coming off eucaliptus trees in the southern hemisphear which has no effect in the states. ;)

pretty sure a no.1 engine failure at that altitude and power would be unrecoverable. or are they catA.:=

wouldnt the temperature at 15' over the desert over compensate for any extra power that might be collected? maybe the blades produce more lift when diverting sand and air downwards??:D

or was he perched on a Train?

I'm just curious - what would be theoretically the best way to handle a no.1 engine failure at that speed and altitude? (I do have a sort of first principles type understanding of rotary theory and controls)

Hope I'm not out of order to ask...

Mac,

For a single engined aircraft such as a Hiller, a slight aft cyclic input whilst initially maintaining the collective position would allow flare effect to climb the aircraft a little, then once it was safe to raise the nose more (tail clearance being paramount) the flare could be increased whilst lowering the lever to enter autorotation.

Full autorotation might not be achievable from such a low height, depending on aircraft type and pilot reaction (probably in the speed/height avoid curve at 15 feet).

For a twin (you said no.1 engine, so I think that's what you meant) the correct response would be similar but once clear of the ground it might be possible to fly away or make a controlled landing, again subject to the above paragraph.

Thank you. Sorry, I did mean a single. Surprisingly, more or less what I had deduced. Presumably there would also be a nasty yaw to deal with as well. Suspect that you'd have to be very quick, very good and very lucky to survive.