Helicopter takeoff

[guru_1071]

Burrow01 said:

Definitely Chickenhawk - they describe flying out of a minefield using this technique

I read this, it was something to do with moving into clear air which gave more lift than just trying to go straight up

it also mentioned one guy who tried this, hooked a load of barbed wire and had to land in the minefield


a great book, well worth a read

[Siko]

guru_1071 said:

I read this, it was something to do with moving into clear air which gave more lift than just trying to go straight up

it also mentioned one guy who tried this, hooked a load of barbed wire and had to land in the minefield


a great book, well worth a read

He was trying to get 'translational lift' by getting speed on from circling as fast as possible before he jumped over the fence. Essentially the power curve for a helicopter is a bit like a 'U' (with a little oddity at the start due to ground effect ) so you use more power to hover or go fast, but in the middle is a happy place. Commonly known as Vy or Vbroc, which equates on my helicopter to about 80kts.....essentially you have the best power margin there and use the least power.....so getting there as quickly as possible if you're hot and high is a necessity.

Commercial air traffic use a different technique, which enables you to reject a takeoff in a known distance. So departures from an airfield are normally started from the hover, where the performance data is known. Bored yet?!

[rhinochopig]

guru_1071 said:

Burrow01 said:

Definitely Chickenhawk - they describe flying out of a minefield using this technique

I read this, it was something to do with moving into clear air which gave more lift than just trying to go straight up

it also mentioned one guy who tried this, hooked a load of barbed wire and had to land in the minefield


a great book, well worth a read

I like the instructor's line about using smaller and smaller fields when the author is struggling to hold a stable hover.

[Geneve]

As said, 'translational lift' is key, which comes into play at about 15kts air speed

Different types of helicopter can have different take-off profiles depending on conditions, but they will almost always want to t/o into wind.

Many twins lift vertically and then climb backwards to c.75 ft, before departing forwards. This is so that, in the event of one engine failure, they can see and return to the original landing spot.

Even helicopters with skids can do a rolling t/o (and landing) on a suitable surface, such as grass. Hot, high and heavy are the usual influencing factors.

[mph1977]

jhfozzy said:

Rolling take off into the wind if possible.

which is why where possible a ship will steam into the wind at a reasonable speed to give a 'headwind' over the landing area

[Prawo Jazdy]

Ships don't need to land. You're talking nonsense!

[maffski]

Prawo Jazdy said:

Ships don't need to land. You're talking nonsense!

http://en.wikipedia.org/wiki/Airship

[JVaughan]

eccles said:

In day to day use Apache's usually do a vertical take off.

All the apache's at Middle Wallop use the 200m purpose made runway for take off. reduces fuel usage. only time you see them taking off vertically is when they are performing precision handling.

[wokkadriver]

Siko said:

I used to fly Merin and Puma (both wheeled helicopters) and we practised running take offs for scenarios when we were power limited;

Like when you'd brought 2 maps instead of 1 or had an extra sugar in your coffee that morning?




;););)

[eccles]

JVaughan said:

eccles said:

In day to day use Apache's usually do a vertical take off.

All the apache's at Middle Wallop use the 200m purpose made runway for take off. reduces fuel usage. only time you see them taking off vertically is when they are performing precision handling.

Just going by what I see day to day at a non training base

[Siko]

wokkadriver said:

Like when you'd brought 2 maps instead of 1 or had an extra sugar in your coffee that morning?





;););)

Busted....!

[RizzoTheRat]

Geneve said:

Many twins lift vertically and then climb backwards to c.75 ft, before departing forwards. This is so that, in the event of one engine failure, they can see and return to the original landing spot.

I believe that's pretty common when using helipads on top of buildings as your alternative options can be pretty limited.

[JVaughan]

eccles said:

JVaughan said:

eccles said:

In day to day use Apache's usually do a vertical take off.

All the apache's at Middle Wallop use the 200m purpose made runway for take off. reduces fuel usage. only time you see them taking off vertically is when they are performing precision handling.

Just going by what I see day to day at a non training base

Speaking to a mate in the "know", "if" a runway is available and they are cleared to use it, they will. Also if they are carrying a full fuel / weapons load, its more economical to have a rolling start.
from what ive just been told its all to do with circumstance