Vortex Ring State Versus Settling With Power.

[Rotor George]

In short, The "Huey Tuck" is a phenomena caused when the helicopter noses over too far on takeoff, the increased wind resistance on the flat top of the Huey forces the nose downwards.

 

Pulling the cyclic back would not overcome the pressure on the roof. Pulling up on the collective added power to the system, causing a higher speed crash.

 

R

[cap]

The 'Huey Tuck'..........Put simply, that roof surface that you walk upon to do all your upper inspections on a Huey is more than that. Present that large, flat surface to the advancing airflow at a somewhat steep angle and the a/c will attempt to lessen that angle. It can only do that by pointing it's nose DOWN to achieve it. If the pilot will not allow that because he is pulling back on the cyclic and hasn't reduced collective a lot, the toes of the skids make contact with the ground microseconds before a M/R blade tip and........

 

 

Done hundreds of feet above terre firma it is an 'eye-opening' experience only as long as one knows what happened and the mechancics behind it. Not manytake-offs are done with that kind of ground clearance by those in 'hot dog mode' or in some kind of a big hurry. Being in light Gross Weight mode does not help the matter either because much more power is available and if you ain't using the max T/O PSI for your type of Huey, then 'things can happen'........AND QUICK!! That MAX T/O PSI is there for a reason and found out about the 'hard way'.....so respect it for many reasons.

 

 

[Guest jacdor]

The 'Huey Tuck'..........Put simply, that roof surface that you walk upon to do all your upper inspections on a Huey is more than that. Present that large, flat surface to the advancing airflow at a somewhat steep angle and the a/c will attempt to lessen that angle. It can only do that by pointing it's nose DOWN to achieve it. If the pilot will not allow that because he is pulling back on the cyclic and hasn't reduced collective a lot, the toes of the skids make contact with the ground microseconds before a M/R blade tip and........

 

 

Done hundreds of feet above terre firma it is an 'eye-opening' experience only as long as one knows what happened and the mechancics behind it. Not manytake-offs are done with that kind of ground clearance by those in 'hot dog mode' or in some kind of a big hurry. Being in light Gross Weight mode does not help the matter either because much more power is available and if you ain't using the max T/O PSI for your type of Huey, then 'things can happen'........AND QUICK!! That MAX T/O PSI is there for a reason and found out about the 'hard way'.....so respect it for many reasons.

 

Excellent and here is a short version of it from the FM

 

If you look in the B205 Flight Manual, there is a chart called "Power limits for take off"

 

The chart is there for that reason.

 

Copy below from the FM

 

The POWER LIMITS FOR TAKE-OFF

CHART is based on power required to hover

in-ground-effect plus an additional increment

of power. The limitations are imposed to

preclude the possibility of unsafe nose down

attitude during the take-off flight path. These

limits shall be observed until 55 knots and

at least 50 feet above the ground are obtained,

after which ENGINE POWER LIMITATIONS

FOR FLIGHT may be used.

 

 

Note

This curve shall be used to maintain safe

attitude during take-off flight path

 

 

JD

[cap]

L3Driver -----sory 'bout that....I completely missed your question which I assumed was directed at me.

 

The exact details of the crash escape me after all these decades, but this much I know. The Hughes 500 basically got the LOH (LOACH) Contract from the US Army because on that day it crashed during it's military test flight, it did so without injury to anyone onboard even though it was substantially damaged. The Army brass considered that a 'survivability factor' because of it's oval egg-shape....and the rest is history.

 

The Bell 206 lost out to the Hughes 500, but an order was placed by the US Army for a number of them and some of those saw service in Vietnam. Unfortunately, at temps of 30+C and RH's of 75-90%, it didn't perform too well. Full tanks and one 145 lb passenger + a very small amount of luggage made the a/c about 100 lbs overgross. It could maintain flight under those conditions only with the N1 reading a constant 104% and never being able to reach 100 MPH. It basically became a joke and logged lots of time just sitting.

 

The Hughes was 'de-rated' and proved to be a fantastic a/c. Regular loads were the pilot and either a gunner in the back with a floor-mounted .50 cal or seats out and up to SEVEN Vietnamese troops crammed into the back. You read this post of mine now only because on more than one occasion the crew of a LOACH made it possible for me to come home.....God Bless them all. Never flew a Hughes 500, but they take no 'bad-mouthing' within my earshot as a result. That's one 'cab-over-chain-saw' that you don't want to mess with and takes a lot to bring down out of the sky in anger.

[splitpin]

The exact details of the crash escape me after all these decades, but this much I know. The Hughes 500 basically got the LOH (LOACH) Contract from the US Army because on that day it crashed during it's military test flight, it did so without injury to anyone onboard even though it was substantially damaged. The Army brass considered that a 'survivability factor' because of it's oval egg-shape....and the rest is history.

You have to love the 500 for survivability. I saw a one of our 500's hit telephone lines in West Africa (Viking ship) Hit the cluster going flat out, snagged the wires on the gear legs, snapped back the cyclic, snipped off the tail boom, and shot vertical spinning like a top to about 300' or so. At that point physics took over and he dropped like a brick. Both guys walked away!! Both seats had collapsed, gear legs were driven into the cabin, transmission dropped about a foot, the rest of the tail boom snapped off and there were a few really good wrinkles on the fuselage. And the most amazing thing of all, she stayed upright. Oh yes, she also caught fire a few minutes later. You should see that keel beam burn. Made out of magnesium it seems.

[twinstar_ca]

once anything from the -ium family begins to burn, you might as well stand back and watch the show!!! :shock: :shock:

 

by the way, splitty... thanks for the heads up on the last spam!!!

[Dewey]

All the really expensive parts of a helicopter are made from unobtainium. These parts just burns a hole in your pocket!

[cap]

jacdor ------- don't mean to be argumentative, but I'm well aware of that part of the 205 FM that you mention. It gives you enough information to be confusing and by that I mean it does not tell you what the a/c will attempt to do if you don't comply. Bell does that all the time and it's either that or no mention made at all of something very important. Example: What's wrong with directions in the FM about how to park a 205 in high winds to keep the M/R from either breaking-off the static stops, bouncing the a/c all over the place or possibly shortening the tailboom? Another example: Why state that the a/c cannot be started with rear winds of a certain speed and leave it at that because.........again that's only PART true. I argued with the Bell rep in Vietnam about that very thing on a very windy day and with my a/c pointing rear-end into that same wind. He said it couldn't be done and I'd 'cook' the 'stove'. I asked my Crew Chief to grab the nearest galvanized garbage-can lid and hold it inches from the tailpipe. He did so, the start was all within temp range and very normal. Did Bell ever put that in any of their FM's or Rules of Thumb books that they used to sell at Ft. Worth? Nope! Just let the 'newbies' on type find out the hard way and in the meantime 'follow that FM and believe that every piece of information that Bell ever learned about that model of Huey is in that FM. Ergo, why all the secrets and why am I passing along information that any Medium pilot in the world should know BEFORE he gets certified-on-type.........AND I mean BASICS?

 

 

 

[cap]

Splitpin----------my 'creeping alzeimers' made me forget to pass-along a funny story just for your appreciation. Don't know if you were in the RCN when they still had S-55's, but if you were you'll apprecaite this even more.

 

When I first arrived over in the 'rice paddies' eons ago, the USMC was still using Sikorskys. They had one crash at our field one day and the pilot was slow getting out. The Vietnamese-crewed Fire Truck arrived almost immediately and reeled-out their high pressure hoses. I saw nothing wrong with all this UNTIL their water started hitting the clam-shell doors, covering the engine. The fire was starting to dissipate, but the second that water hit those doors, the whole nose exploded in massive flames. The crews all dropped their hoses, got into their trucks and sped away quickly like the Keystone Cops, expecting the a/c to explode. My Crew Chief was bent-over and laughing his fool head off. I asked him why and he tried to explain that those doors were made of phosporous metal and that they just LOVED water..........then I started a belly laugh also. Your mention of the 500 beam brought all that back again. I laughed again heartily and I'll think of that all day now and walk around with a silly grin on my mug. Thanks for that bud.

[Guest jacdor]

jacdor ------- don't mean to be argumentative, but I'm well aware of that part of the 205 FM that you mention. It gives you enough information to be confusing and by that I mean it does not tell you what the a/c will attempt to do if you don't comply. Bell does that all the time and it's either that or no mention made at all of something very important. Example: What's wrong with directions in the FM about how to park a 205 in high winds to keep the M/R from either breaking-off the static stops, bouncing the a/c all over the place or possibly shortening the tailboom? Another example: Why state that the a/c cannot be started with rear winds of a certain speed and leave it at that because.........again that's only PART true. I argued with the Bell rep in Vietnam about that very thing on a very windy day and with my a/c pointing rear-end into that same wind. He said it couldn't be done and I'd 'cook' the 'stove'. I asked my Crew Chief to grab the nearest galvanized garbage-can lid and hold it inches from the tailpipe. He did so, the start was all within temp range and very normal. Did Bell ever put that in any of their FM's or Rules of Thumb books that they used to sell at Ft. Worth? Nope! Just let the 'newbies' on type find out the hard way and in the meantime 'follow that FM and believe that every piece of information that Bell ever learned about that model of Huey is in that FM. Ergo, why all the secrets and why am I passing along information that any Medium pilot in the world should know BEFORE he gets certified-on-type.........AND I mean BASICS?

 

 

Hello Cap

 

You are right here and no doubt about it. In my earlier post I simply pointed out your excellent explanation of the phenomena and added to it that in the FM there was a chart for that reason.

The reason I made a relation to that chart is that NOT many pilots were aware of it in relation to the "Huey Tuk" phenomena which is NOT explained in the book excepted for "it could be a unsafe attitude" and not saying why.

You mention this chart to a young medium pilot and in general he won't have a clue of what you are talking about.

Simply thought that adding this after your explaination would send some pilots back in the book and reread the chart WITH an understanding of the reasons behind it and a new point of view on the matter.

I have never experienced that condition myself but I sure experienced other phenomenas peculiar to the Bell Mediums or helicopters in general, like high speed blade stall but that is another story.

 

Have a good day

 

JD