Undercarriage Bolted Down for Offshore Flight

[gnow]

I would like to know from some other operators whether they allow an aircraft to go offshore if the undercarriage is bolted down for some reasons. Although the MEL says an aircraft can be flown with its gears bolted down, I personally feel that it SHOULD NOT be used for over water flying as the ditching drill calls foe gears UP. If the gears were down, the chances of a capsise during the touchdown process if there is forward speed is ver great

[Shawn Coyle]

Not sure of the model, etc.
Need to check the MEL for that sort of thing. It should have something about landing gear bolted down and floatation. If not, I'd check with the manufacturer pretty quickly.
I doubt that having the gear down in a helicopter in ditching would make the chances of capsizing significantly worse than they are already, as the forward speeds should be very low on touchdown.

[leading edge]

I have to agree with Shawn Coyle.

The forward speed of a helicopter on ditching should be low enough as to not have any "digging in effect"

On most wheeled types (S61, 332L and S76) I would select the gear down anyway to give more weight to the lower part of the aircraft and to maximise stability when floating as much as possible.

Most helicopters are top heavy and anything which lowers the weight in the water would be positive in my opinion and reduce the chance of a capsize during evacuation.

[AirJockey]

Don`t know if I understand your Q. with bolted down, but most Bell products have fixed landing gear. Sure the FM on some retractable landinggear machines advice you to leave them up in case of ditching, but like Shawn Coyle says, in case of ditching your speed should be quite low anyhow.

[HughMartin]

This is not an uncommon event in the North Sea if there is a fault with the u/c retraction/extension system.

As to ditching, I would agree with previous posts regarding insignificant effect on the actual ditching process but improving stability on the water.

I don't have any evidence to back up this view as I am not aware of any trials being carried out. As far as I know the only trials relate to a/c stability on the water and not to the actual ditching process itself - and these are only with scale models.

I'd rather have the gear locked down than locked up.

[212man]

The ditching aspect is not very significant; more important is the flight planning, on some types.

e.g. On the 76 you need to enter the Cat A graph 1000 ft above T/O altitude, which has some impact. Aditionally the TAS/FF ratio will change significantly.

Even on types with low drag gear, such as the 332 there will be some effect (maybe 5% more fuel). A few years ago a certain UK operator had a gear collapse on a diversionary landing; the gear was selected up after T/O but did not retract. This was not noticed, but the reduced TAS/increased fuel burn was and the diversion made due to low fuel predicted at destination. The gear collapsed on landing with the selector still up (lots of CRM issues too, e.g. checklist use).

[AirJockey]

In certain wave conditions you might be better off leaving the gear retracted due to the strong wave currents passing under the machine. With gears extended and the helicopter 90`to the waves the chances for capsizing "might" be greater than with gear up due to the drag they produce in the water, even though they don`t stick that far out. Top heavy machines are not helping either.
This might be the reason why the FM states leave gear up during ditching?

Anyone disagree?

[Red Wine]

Would be an interesting exercise to see a S76 land on water without its wheels down due to the floats being in the wheel wells??

[Steve76]

........I was just thinking the same thing Red Wine.
Regardless of whether you ditch with wheels down or not by the time you blow the floats and the explosive link you will have plenty of helicopter in the water. I doubt having the gear up will make any difference. Having the doors shut means a delay in the inflation process and what happens if the link fails?

[Ascend Charlie]

Another problem with the 76 is that if you have popped the floats with the gear up (it will still work, the explosive bolts disconnect the doors from the gear) and you then select gear down, you will poke holes in your floats.

And to answer Air Jockey's question, wouldn't it be better to have some weight below the floats to stabilise it better? If the cg is high, it will tip over easier. But I believe the 76 settles reasonably well into the water and the doors will still open OK.

[SASless]

212man's outfit flew 76's with the gear bolted down until the question was raised...whether that was advisable. The occasional flight that way might not hurt but the doors are not designed to be operated that way indefinitely and thus are not stressed nor tested for that operation. It would seem the engineering effort on fixing the gear problem would be more appropriate than merely bolting the gear down.

[Red Wine]

Hope you are all HUET and HABD/HEEDS Current....????

Would not leave home alone without mine!!!!

[gnow]

I think you guys got the message wrong. The helicopter will have a very good chance of flipping over due to the moment created by the undercarriage if it is bolted down. However, I do agree with you all(in fact it is in the check list) that the gears MUST be down after ditching. I am involved in water sports and over the water even 20 knots is a lot of speed.The water feels like concrete at 20 knots.

[leading edge]

Then, why ask if you already "gnow" the answer.

I think you got some good replies here. Anyway, if it's a skid type, what are you going to do? Blow the skids off?

Maybe they should be banned from overwater flying according to your reasoning.

Just tell your company that you refuse to fly if the gear is bolted down and solve "your" problem.

I think you are wrong and most of the others here are right..but that's just my opinion.

LE

[cyclic]

One of the guys who did the Canadian waterbirds course where they stick a Sea King in the water deliberately, told me that they "landed" gear up and gear down and it made little difference - obviously they weren't shutting down! They did one running take-off and realised they had left the gear down once they had got airborne which I thinks demonstrates how little overall additional drag there would be if you were to ditch with forward speed.

I have spent many hours over the sea with retracts and it never concerned me if we were forced to fly with the gear locked down for some reason. I now fly over the sea in a skidded aircraft and I don't think they would make a jot of difference in a ditching situation - hope not to find out though!

[Gomer Pylot]

gnow, didn't you read the post in which it was made rather clear that you can't blow the floats with the gear up, then put the gear down without puncturing the floats, at least on the S76?

Why you believe that the gear being down will make the helicopter roll is beyond me. I would always put the gear down before ditching in an S76. And the S76 has an airspeed limitation with the gear down, and the doors are certainly stressed to withstand flying for any period below that airspeed. In short, going offshore with the gear pinned down is not a problem, as long as the fuel and airspeed limits are planned for. Some types might present some problems, but the RFM and MEL should tell you what those are.

[Red Wine]

We seem to be talking about the worst case scenario now…an engine[s] off landing on the water. The ideal is a zero/zero landing on the back of the wave, so talking about forward speed at impact is a nonsense.

The more common occurrence would be a precautionary landing with engine[s] running, fuel, gearbox, vibration, lighting damage, your mind can imagine another bunch of things…..then in this case, inflate the floats in the hover and land.

[John Eacott]

Gnow,

Totally disagree that "the will have a very good chance of flipping over due to the moment created by the undercarriage if it is bolted down".

Retractables are a relatively modern introduction in the helicopter world. Overwater flight, and ditchings, with fixed undercarriage have gone on for decades; either the whole airframe digs in and turns turtle, or the pilot flares to a near zero airspeed, as taught, and pops the floats. U/C position has little effect on the outcome.

Spot the difference: the only thing I recall is that the brakes didn't work too well.....

http://www.helicopterservice.com.au/photos/pprune/S61N%20water.jpg


http://www.helicopterservice.com.au/photos/pprune/S61N%20water%20landing%2001.jpg

[NickLappos]

For an S-76, Mox Nix IMHO.

The gear down is not a water entry problem, it robs about 6 knots speed (and thus about 4% range) and little else.

If the MEL for your country allows it, march on, and plan the gas right.

Of course, it would n\be nice if things were fixed on your hel

[SASless]

Nick,

Did youse guys in snowy Connecticut doing any testing on prolonged flight operations with the gear down on the 76 or just limit it to confirming airspeed limits as designed?

I thought the conventional wisdom around the Sikorsky shop was that flying with the things bolted down on the 76 was operating them in a manner that lay outside the design concept and thus was a walk on the wild side over time.

I wholeheartedly agree that returning the aircraft to a completely serviceable and air worthy condition beats the practice of seeing just what the aircraft can fly without.

[Red Wine]

What impact would constant exposure of the float bags have with, rain, hail, snow, sea water spray and abrasive dust????

[ATN]

The 365 N RFM reads that ditching with LG up or down does not make any difference. On take off we retract it right after rotation to get a better ROC on one engine.

ATN