View Full Version : Rain: how does it affect our helicopters?


Brilliant Stuff
20th Jul 2007, 08:20
How "bad" is rain for our helicopters? After all those blades will be "hitting" the rain drops at a fair old lick and we all know how a pressure washer works. It does take care of those pesky squashed bugs though.

Are helicopters tested during downpours? I mean has there been some thought put into design how to deal with the masses of water entering the transmission deck etc.?

Certainly our wipers won't cope with much and they can not be used at cruise-speed.

What can our "test pilots" tell us?


Regards BS



teeteringhead
20th Jul 2007, 08:50
Always surprised me that helicopters - even with flat screens - that generally go slower than Porsches can have worse windscreen wipers!

Never thought I'd meet an odder wiper than the manifold underpressure driven one on my old Ford Anglia - put yer foot down to overtake in the rain .... and it stopped!

Then I met the Wessex and it's electrical/hydraulic/mechanical wipers - driven by its own electrical pump between the feet of the other pilot, with drive via Bowden cable to the wipers - so any sort of failure would stop it!

Best game was a pump leakage in the rain - guaranteeing that the only pilot who could see where he was going also had his feet swimming in hydraulic fluid......

..... and you were also always certain why Westland never built submarines......

nodrama
20th Jul 2007, 10:15
Mr blade stainless steel leading edge will cope with the rain upto a point. Watch for pitting (and eventually pin-size holes) at outboard leading edge. Sacrificial polyurethane leading edge tape is used sometimes to extend the life of MR blades. Works well but will not survive long being continuously battered by heavy rain (e.g. tropics).

Although not ideal for power, your compressor blades are getting an unscheduled rinse.

Rain can play havoc with avionics. The integrity of cowling/ fairing seals is important to keep moisture away from the wiggly-amps and black boxes.

Unblocked drainholes in the transmission decking will allow the floods to drain harmlessly away. Unblocked drainholes in the lower fuselage and cowlings will prevent 'pooling' and corrosion.

Wipers? They are getting better on some of the newer helicopters, still always seem to be a bolt on after-thought to me.

Flying Bull
20th Jul 2007, 10:30
Hi all,
havenīt flown any helicopter, that was waterproof anyway. After some time it starts to rain into them. Either from the top or through the doorseals.
The 206 doesnīt have a wiper - and as long as you keep the speed up and the windshield polished with nanofluid - no problem anyway.
On the others - wipers seem to make the problems worse - just open the sliding window on the side, accept some water through the window - it will leak out through the doorseals anyway and do some sideslipping i.e. for landing and so on.
Best is flying at night with NVG. You just donīt see the rain, the drops donīt fit to the wavelength of the amplified light. Only the visible range is decreasing and giving you a hint - or reflections from the strobelight.
If you switch on the landinglight - you will see the rain - but better keep it switched off - its blinding then.
Greetings Flying Bull

helimutt
20th Jul 2007, 14:59
happened during very heavy rain a couple of weeks ago, offshore.

http://i30.photobucket.com/albums/c309/kissmysquirrel/blade1.jpg

Brilliant Stuff
20th Jul 2007, 17:03
The Dauphin's I used to fly could make it rain inside the cabin on to the passengers and the the avionics fortunately though they never shorted out on us. Good thing the Pax were already wearing dry suits:E

The current steed is very good at keeping us dry and you can defog the windscreen which you could not with the dauphin which meant we were IFR taxiing out which did not impress the CAA much. Was anything done about it? NO!!!

Well thanks anyway guys.

Regards BS

Noordzee Cowboy
20th Jul 2007, 17:24
I used to fly around heavy showers when i could so i didn't upset the techs by loosing to much blade tape.:zzz:

T4 Risen
20th Jul 2007, 17:37
Why do you think North sea guys get immersion suits...nothing to do with ditching, more to do with machines that leak like a sieve. Super Puma's do not like being shut down off shore in the rain, i have had a couple of experiences when having shut down over night, after a heavy shower or worse a sea fog with a bit of wind behind, moisture has got into the aircraft and next morning, press the button and nothing....not even a click. you would think that a multi million pound helicopter would at least be able to keep a bit of rain out.
T4

ShyTorque
20th Jul 2007, 20:31
On the others - wipers seem to make the problems worse - just open the sliding window on the side, accept some water through the window - it will leak out through the doorseals anyway and do some sideslipping i.e. for landing and so on.

Assuming there is a sliding window, of course! Some types ( A109, for example), have only a fixed window panel.

The military Puma was bad, when parked in rain it used to collect a pint of cold water in the window frame which would dump down your right leg and into your boot when you lifted to the hover. The radios and intercom used to fail completely, usually in IMC, due to water ingress into the nose avionics bay, hence the use of "black bodge tape" over the panel edges in an attempt to seal it. In the days before the polyvalent intake filters were fitted, when it came unstuck (usually in rain!) it was likely to go up the nose and into the open engine intakes. Seeing a recent example made me smile - even after the "modded panel seal Mk2" it's obviously still a problem as this one still sported the characteristic old-fashioned black square of tape on the nose panel!

Every S-76 I've flown leaked water onto the pilots from above - most pilots use laminated charts over their legs as aprons when it rains!

RVDT
21st Jul 2007, 06:13
If the aircraft is in the "Transport Category" Part 29 I think you should be aware of this - both operators and maintainers -

For each pilot compartment --

(a) The compartment and its equipment must allow each pilot to perform his duties without unreasonable concentration or fatigue;

(b) If there is provision for a second pilot, the rotorcraft must be controllable with equal safety from either pilot position. Flight and powerplant controls must be designed to prevent confusion or inadvertent operation when the rotorcraft is piloted from either position;

(c) The vibration and noise characteristics of cockpit appurtenances may not interfere with safe operation;

(d) Inflight leakage of rain or snow that could distract the crew or harm the structure must be prevented.

[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as amended by Amdt. 29-3, 33 FR 967, Jan. 26, 1968; Amdt. 29-24, 49 FR 44437, Nov. 6, 1984]To me that means "Thou shall not leak".

I know the current ECD machines are put into a spray rig to be sure they don't leak. 135 doesn't have to comply but the 145 does.

And you are also required to have a side window in this category.

(a) Nonprecipitation conditions. For nonprecipitation conditions, the following apply:
(1) Each pilot compartment must be arranged to give the pilots a sufficiently extensive, clear, and undistorted view for safe operation.
(2) Each pilot compartment must be free of glare and reflection that could interfere with the pilot's view. If certification for night operation is requested, this must be shown by night flight tests.
(b) Precipitation conditions. For precipitation conditions, the following apply:
(1) Each pilot must have a sufficiently extensive view for safe operation --
(i) In heavy rain at forward speeds up to VH; and
(ii) In the most severe icing condition for which certification is requested.
(2) The first pilot must have a window that --
(i) Is openable under the conditions prescribed in paragraph (b)(1) of this section; and
(ii) Provides the view prescribed in that paragraph.
[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as amended by Amdt. 29-3, 33 FR 967, Jan. 26, 1968]


Failure to comply means the aircraft is U/S unless otherwise there is some condition to cover these aspects which is approved.:=

Go and cover all the windows on your aircraft sometime and fly it purely by reference through the "open" side window!!

PS helimutt - Maybe its just the photo but the rest of that 76 looks like a "bucket of bolts" as well!

helimutt
21st Jul 2007, 11:44
It's been MS Painted to hide the name on the side. It does have over 14000hrs, tough offshore life and about 40000+landings, and is 15+years old I think. S76's do leak badly. Surprising when they cost so much to buy. :)

206Fan
21st Jul 2007, 12:39
T4 Do yea pilot AS332s yourself??

I was up doing the lesson last sat in the 22, heading back we got pounded by very heavy rain, i was flying at the time, instuctor let me keep flying through it to see was i gona apply any abrupt movements to the cyclic when she was blowing about by the wind but i just kept the cyclic at were i had it before the rain hit us so all was good, but we couldn't see a dam thing for 5 mins or so. Anybody know if the R22's take kindly to heavy rain??

helimutt
21st Jul 2007, 13:53
if you couldnt see a thing for 5 mins then you were flying illegally. The R22 doesnt leak too bad actually. Only at the doors.

206Fan
21st Jul 2007, 16:01
It was only an expression, seemed like 5mins in the air, was only about a minute or so until we got visibility again.. Aye them doors don't look very tight to prevent rain getting in!

T4 Risen
21st Jul 2007, 21:23
Davy07 yes i do and have done for quite a while, great machine but when it rains, as it does on the North sea very occasionally, you do appreciate the immersion suit!!! :)

TiPwEiGhT
22nd Jul 2007, 17:19
Flying the other day I found that the rain was not coming off the screens and 125kts, the screens were abit mucky with the days flying. What is the best stuff to put on the screens to get the rain off in-flight? Rain-X? Thanks.

Bravo73
22nd Jul 2007, 17:44
Rain-X is good for glass. Not so good for perspex though - can make it cloudy.

206Fan
22nd Jul 2007, 18:17
Davy07 yes i do and have done for quite a while, great machine but when it rains, as it does on the North sea very occasionally, you do appreciate the immersion suit!!!

Ah excellent, i love the pumas thou have never been up in one, just see alot of the RAF Pumas round here, well i did not any more. You fly bristows rigs? Is there any puma simulators about the public can take a whirl in??

TiPwEiGhT
22nd Jul 2007, 18:19
What would be suitable for perspex?

We have just been using an aircraft cleaning solution (suitable for perspex) but it seems to attract the dirt!

Thanks for the response.

Brilliant Stuff
22nd Jul 2007, 18:23
What about the windscreen cleaner by Autoglym?

Bravo73
22nd Jul 2007, 18:37
What would be suitable for perspex?


Aha, the devil's in the detail! ;)

I said that Rain-X can make it cloudy, not will make it cloudy. (They warn as such on the label.)

Test it on a little corner or a side window. The type of perspex on your aircraft might be one of the non-cloudy types.

It can, however, be bit of a faff to apply properly. You are meant to rub it in relatively vigorously so that it effectively penetrates the top layer of glass/perspex. If you just apply it lightly, it will be washed off in the first couple of showers (believe it or not!)

500e
22nd Jul 2007, 22:08
And there's me thinking newer designs don't leak, the 500s leak around the perspex pretty well , used Captain Tolleys Creeping Crack Cure (the original)starts like water then thickens to a clear flexible seal, it stopped most on the first go,when initially applied excess can be removed for about 10 minutes with damp cloth. :D
Have always used Pledge to polish the perspex, it appears to be the polish of choice for a lot of pilots in US

Tailboom
23rd Jul 2007, 20:03
The best polish to use on the perspex and the rest of the helicopter is Autoglym's Super Resin polish easy to apply and get off