PPRuNe Forums - View Single Post - constant speed or variable speed approach
Old 30th Jun 2020, 11:52
  #16 (permalink)  
FH1100 Pilot
 
Join Date: Nov 2006
Location: Pensacola, Florida
Posts: 673
Originally Posted by Ascend Charlie View Post
I think he is asking about a visual approach to a landing site, rather than an instrument approach.

I always did it at an apparent walking pace over my toes. At 300' it equates to 60kt, having selected the hover attitude. Hover attitude, walking pace over the toes, controlled rate of descent.
As the descent continues, the speed bleeds off.
Around 30kt the power starts to come in, a gradual change to the ah-send of the power curve, holding the attitude steady, not letting the secondary effect of collective kick the nose up. Hold the hover attitude, same walking pace over the toes, and you end up in ground effect at walking pace, about to stop, and knowing that you have the power to terminate.

The problem with a 60kt approach is not knowing if you will fall through at the bottom, either through slow response from the engine, or insufficient power available. The pax might not appreciate the rapid flare upwards, the rapid roll-over to level, the rapid increase in engine noise, and the rapid increase of metal tearing itself to bits around them as you misjudged it.

And anyway, if you are on an ILS, your autopilot should be slowly reducing your speed from 120kt to 70kt without you having to activate a brain cell.
Hate to reuse someone's entire post, but Ascend Charlie just makes a whole lot of sense.

When I began working offshore for PHI, I was a "field ship" which is one that is assigned to an offshore post for the seven-day "hitch" and bounces around between a specific group of platforms all day long. My "worst" job assignments had me doing 70-100 landings per day. At first, my philosophy was "every approach an autorotation." I'd come screaming in at 60 knots all the way to the flare. Worked great, and they were fun, but my timing had to be exquisite - which it was, through practice. I was young back then.

Eventually I realized that turbine engines are pretty reliable and we don't have to constantly worry about them quitting on landing. Pilots fail more often than engines. I worried about my timing; sooner or later I would screw up. So I got slower and slower. Now, I do it the way Ascend Charlie describes - nice and gentle, stable, no big power changes (if any) at the bottom. My alternate way is to do like Robieeeee and "ride the ETL burble" down. Or just above it. Keep your spot constant, don't look at the gauges, just keep the cabin level, and don't let the nose come up as you squeeze the power in (common mistake). Easy-peasy. If you do nothing, the ship settles onto its ground-cushion without any mucking about by you. If you screw up and get below ETL early...well, so what? Just keep it coming down gently.

In 15 years at PHI, almost all of that offshore, I did six or seven landings per hour to elevated offshore helidecks. Times 5,000 hours, that roughs out to, ohhhh, 30,000 or so landings on oil platforms/rigs. And over the course of that time, I sure learned what *not* to do on an approach.

Lots of great info in this thread.
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