Helo Funnies

[daepp]

So Seahawk, the helo was using so much power just to hover that there was not enough tail rotor to keep it from spinning? Did the addition of water stop the spin?

Don't all helo's have enough power to hover? I know I am missing something here -sorry.

[crustychief]

It was a hot day and high altitude. ( the air was thin )

[Seahawk]

Originally Posted by DAEpperson

So Seahawk, the helo was using so much power just to hover that there was not enough tail rotor to keep it from spinning? Did the addition of water stop the spin?

Don't all helo's have enough power to hover? I know I am missing something here -sorry.

Crusty has it right....every helo has performance parameters that take into account environmental factors such as Density Altitude (affected by heat, humidity, etc.: the density of the air) . For instance, at sea level on a very hot, humid day in Florida, the helicopters engine(s), main and tail rotor may see a Density Altitude of 2500ft, meaning even though the helo is at sea level, it will perform as if it was at altitude.

Weight is also a huge factor.

The term is, "high, hot and heavy", all four letter words

Lake Tahoe is at 6200ft above sea level...add heat, humidity and a heavy helo and you've got a fairly tight performance curve for hover, both in and out of ground effect.

I also know a few folks at HSL-41 (I went through there in the 80's) and it is clear they gooned it. I came very close to doing the same thing as a JO, so I do understand.

[crustychief]

I can't wait to read what Grampaw Pettibone says about it.

[avi8torny]

Seahawk.....was it a high DA day??? I would think that a 60 could hover IGE, I know they're heavy but jezz. School me on this one.

[944Larry]

I flew a helicopter on floats and didn't like it at all. This really gives me the heeby-geebies watching this.

[Joeaksa]

Originally Posted by avi8torny

Seahawk.....was it a high DA day??? I would think that a 60 could hover IGE, I know they're heavy but jezz. School me on this one.

Performance is figured at sea level and a 59f (15c) day. Every foot you go above sea level the performance drops, and every degree warmer the same thing, resulting in a DA of say 9000 feet at a lake that is at 6200 feet.

A hover OGE is one thing at sea level, and a DA of 9000 or even higher is another.

[pbflyz]

Originally Posted by crustychief

I can't wait to read what Grampaw Pettibone says about it.

Ha! That's a blast from the past.


"Dagnabbit, these fellas went a joy-ridin' and darn near roon'd a couple perfectly good helo copters..."

(Granpaw Pettibone was a mishap review column in the Naval Air safety magazine, "Approach.")

Looking back, I did some pretty dumb things flying for the Navy, but luckily, never actually bent an aircraft. I was lucky, but it sounds like these guys may be walking for awhile.

The Humiliation Triangle:

Wrong Place
Wrong Time
Witnesses.

[xlr8]

Sikorsky S-70 - Wikipedia, the free encyclopedia
History : Weather Underground
Density Altitude Calculator
http://www.faa.gov/library/manuals/aircraft/media/faa-h-8083-21.pdf

Wiki reports hover out of ground effect-4300'. In ground effect-9000'
Wx at South Lake Tahoe shows wind speed and direction varied throughout the day.
Density altitude as much as 8316'.
There is a brief description of Loss of Tail rotor Effectiveness at altitude in the FAA Rotorcraft Handbook chapter 11, page 13.

[avi8torny]

Originally Posted by xlr8

Sikorsky S-70 - Wikipedia, the free encyclopedia
History : Weather Underground
Density Altitude Calculator
http://www.faa.gov/library/manuals/aircraft/media/faa-h-8083-21.pdf

Wiki reports hover out of ground effect-4300'. In ground effect-9000'
Wx at South Lake Tahoe shows wind speed and direction varied throughout the day.
Density altitude as much as 8316'.
There is a brief description of Loss of Tail rotor Effectiveness at altitude in the FAA Rotorcraft Handbook chapter 11, page 13.

Hover IGE for a -60 has got to be more than 9000'.

[xlr8]

http://www.sikorsky.com/StaticFiles/Sikorsky/Assets/Attachments/Mission%20Downloads/S70-061_IBH_SS.pdf

Here is the source.

[xlr8]

Helicopter Aviation
"Maximum ground effect is accomplished when hovering over smooth paved surfaces. While hovering over tall grass, rough terrain, revetments, or water, ground effect may be seriously reduced. This phenomena is due to the partial breakdown and cancellation of ground effect and the return of large vortex patterns with increased downwash angles.
At a rotor height of one-half rotor diameter, the thrust is increased about 7 percent. At rotor heights above one rotor diameter, the thrust increase is small and decreases to zero at a height of about 1 1/4 rotor diameters."

[dhoward]

Thanks Paul. I like a good helo story.

[daepp]

Ok, for the idiots here like me, a helo hovers differently near the ground (ground effect?)?

[Joeaksa]

Originally Posted by DAEpperson

Ok, for the idiots here like me, a helo hovers differently near the ground (ground effect?)?

Yep. Its called "hover in ground effect" or "hover out of ground effect."

In ground effect, in other words close to the ground, you get more lift. Outside of OGE you get less lift.

Will let the helo guys explain it more. I push forward on the throttles and as we pass mach 1 we get all the lift we need!

Joe A