Gross Weight

[TimW68]

I am a private pilot and have a couple of questions with reguards to a comment I heard in passing. How often are ships required to take off from the platforms (rigs) at gross weight, I mean is this a very common thing? The comment i heard was that on occasion ships had to skid along (on the pad) to get ETL, due to WX/weight, is this true and if so has anyone heard of any inadvertant tail strikes due to misjudgement?

[Gomer Pylot]

Taking off at max gross weight is very common. But if you can't hover, then you aren't going to take off. Back when piston powered ships were in use, it was fairly common to drop off the side, but we're well past that. You may not be able to do much of a climb, but you have to be able to hover and get off without immediately losing altitude. The usual technique is to hover at the edge of the pad, with the blades over the water, and hold a very stable hover. Eventually you'll get enough updraft to start a takeoff, and you just go up and out, perhaps losing altitude as you accelerate. If you can't hold an absolutely stable hover, moving nothing at all for a minute or so, then you may not be successful. If you're moving the controls around you'll lose lift every time you move them. If you can't get the lift to come up, then you reduce the load, one way or another.

[helonorth]

Common to take off at gross weight, but no running take-offs from the platform! (or anywhere

else). If you can't keep a stable hover, someone gets off.

Edited June 14, 2008 by helonorth

[JDHelicopterPilot]

Agreed. If you can't hover IGE, don't try a take off! I don't even think there is enough room to do a running take off and to be able to get ETL on a platform. I know there wasn't from the platforms I flew from anyway.

 

There are times you may loose a little altitude but in general just take it nice and slow and easy. Don't be abrupt on the controls. As GOMER said the more you are moving them the more lift you are diverting away. Remember, if it's hot out and your have a high PA your density altitude will be high. Consult your aircraft performace charts before flying.

 

Flying at max gross weight is the name of the game for operators. They want to maximize their dollar and one way to do that is to put the flight at max gross weight given the conditions outside.

 

JD

[TimW68]

Thank you for the great answers, it really helps to tap the experience!

[Wally]

Been awhile since I flew the Gulf, ten years. Old guy observations:

The customer and the company want the same thing, max performance. One, to get the most bang for the buck, the other to deliver the best service profitably. The profit part means having almost enough aircraft performance for the occasional demand, but no more than you need most of the time. Flying with everything one could legally and practically take is not unusual.

I never, ever saw a running takeoff offshore. The decks aren't big enough to get a good head of steam up on (get to ETL). And, there's too much stuff poking up to snag a skid, even on metal helidecks in good shape to make it a tempting proposition.

Ground effect seems to evaporate too quickly as I came off the edge in rush for me to ever try the dive off thing. I did that once, and I know my tail was clear, but not being able to see it, and knowing a miscalculation in that regard would be a very bad thing, so that once was it. NO cheating on the numbers or if I couldn't get a stable hover to possibly transition off the platform, then somebody's waiting for the next lift, and it's not my problem.

That said, I liked offshore better than beach flights. Once you cleared the structure and deck, one was pretty much home free, offshore. Some beach bases stretched that out. I remember nursing many a Ranger and Longranger down Bayou Lafourche out of the old Leesville base beause there were wires and buildings in both upwind quadrants, a little crosswind carefully worked was necessary to get to ETL at gross, as one skimmed the water or marsh... Some bases were even worse.

[Gomer Pylot]

The old Tenneco base at ICY was a bad one, with big trees all around it. That's about the only place I ever used the water/alcohol injection in the L model. Not long enough to get a really good run, you just had to pull all you had to get over the trees, and then get to the intracoastal waterway.

 

But the absolute worst helipads I've ever flown in or out of are hospital pads. Idiots designed most of them, and idiots still maintain them. It's no wonder there are lots of accidents at hospital pads. And we just accept these hellholes as business as usual.

[Wally]

The old Tenneco base at ICY was a bad one, with big trees all around it. That's about the only place I ever used the water/alcohol injection in the L model. Not long enough to get a really good run, you just had to pull all you had to get over the trees, and then get to the intracoastal waterway.

 

But the absolute worst helipads I've ever flown in or out of are hospital pads. Idiots designed most of them, and idiots still maintain them. It's no wonder there are lots of accidents at hospital pads. And we just accept these hellholes as business as usual.

 

Amen, Brother! Except, I think you're overstating the idiocy of design- most have NO design at all, just a painted "H" if anything. It's a carefully considered plan in many cases. I'll leave it at that.

P.S. Were you flying ICY Tenneco when they had the 4 "Bob" pilots on the same shift? The call would be "Send the 'Red Bob'", or "California Bob"...

[Gomer Pylot]

I don't remember that. I didn't fly Tenneco very long, just filled in a few hitches before Lee Bundy talked me into going out to VER26. Pulled me on like an old boot, but I did learn to land a 206.

[joker]

On another tack, we are bound by very strict regulations for our Cat A flight regeime.

 

We do a Vertical Cat A departure and are forbidden any drop down below 35' above deck level if OEI. (Even though we are launching off elevated helidecks.)

 

The therefore rather than the normal S76 max gross of 11,700lbs, we are restricted to 10,500lbs as our MTOW.

 

The two diagrams on Page 4 of this PDF show the differences in Cat A departure profiles.

 

http://www.faa.gov/library/manuals/aviatio...ia/appndxC1.pdf

 

Maybe if some of your hospital helioport designers had read this document, you wouldn't have such a problem!

 

Joker

Edited June 18, 2008 by joker

[Gomer Pylot]

They never read anything, they just stick a pad somewhere as an afterthought. We've actually volunteered to provide design input, but were rebuffed by the hospitals. In any case, there are no Cat A departures being done. You cannot do Cat A procedures in a single-engine aircraft, few multi-engine EMS helicopters can do them anyway, and the departure pad has to be surveyed and certified before it's even possible to do a Cat A procedure. Where are you doing Cat A?

 

BTW, your link only references IFR, not Cat A takeoff procedures. Did you perhaps post the wrong one?

Edited June 18, 2008 by Gomer Pylot

[joker]

BTW, your link only references IFR, not Cat A takeoff procedures. Did you perhaps post the wrong one?

 

Seems like I did! Don't know how the other one got there, but here's the one I meant.

 

Really looking for the diagrams on P.4 to help anyone understand what a vertical departure profile looks like.

 

http://www.flightsafety.org/hs/hs_sep-oct92.pdf

 

Flying in Asia.

 

Joker

[Cowboydave157]

The old Tenneco base at ICY was a bad one, with big trees all around it. That's about the only place I ever used the water/alcohol injection in the L model. Not long enough to get a really good run, you just had to pull all you had to get over the trees, and then get to the intracoastal waterway.

 

But the absolute worst helipads I've ever flown in or out of are hospital pads. Idiots designed most of them, and idiots still maintain them. It's no wonder there are lots of accidents at hospital pads. And we just accept these hellholes as business as usual.

 

Gomer,

 

"water/alcohol injection in the L model" Please explain?

 

Cowboydave157

[Gomer Pylot]

The original 206L had a C20B engine, the same as the B, and it was very underpowered. In order to allow takeoff under hot and heavy conditions, there was a small tank in the baggage compartment that had a mixture of water and alcohol. There was a switch on the collective which operated it. The tank was pressurized by engine bleed air, and when the switch was turned on, the water/alcohol mixture was injected into the engine intake, cooling the TOT by close to 100 degrees. If you started a takeoff and saw that the temp was going to go over the redline, you flipped the switch and the temp immediately went down. There was enough mixture for about 3 minutes, and you had to hoard it, because you might have to fly all day before you got back to the base for a refill. It usually only took a few seconds, and then you could reduce power enough to get the temp back into the yellow. One poor soul had maintenance put pure alcohol into the tank by mistake, and when he hit the injection, everything went over the redline, by a lot. Most of the moving parts became scrap on the spot.