Flying in cold temps

[flyheli]

What's the lowest temperature you can/should fly around.... what's the first limiting factor?

[paco]

First look in the flight manual - the AS 350 starts at -40C, for example.

Otherwise, it depends on whether the heater works, I guess!

Phil

[Deiceman]

What's the lowest temperature you can/should fly around.... what's the first limiting factor?

Limiting factors can include the temperature where the various seals or gaskets no longer seal or gasket, or something as simple as the coldest day found during certification testing. VNE can be driven by tip Mach Number.

Remember, cold soak starting and operating temperatures may be different.

[Shawn Coyle]

But beware - many older machines (certified under the old CAR 6 rules) didn't need to specify a minimum or maximum temperature for operation.
Not sure what advice to give in that situation!

[MINself]

I don't know about the aircraft but my limits for enduring the cold were always hit first, normally at about -20 C still air.

One of the types of aircraft I had the pleasure to fly in the Artic peformed very well once you got it up and running but that was just the thing we had minimum temperatures for starting engines to ground idle (-26 C or more indicated temp of the engines, my memory is a little bit hazy here, I think this was an oil temp prior to start springs to mind) and then limits for setting them to fly (again -10 C indicated temp, possibly oil temp) I never saw temps this low as we hangared them in heated hangars at night.

There were a whole load of other factors concerning the transmissions too. I never came across it but we had to change the oil we used once we went Oop north because of something called coring and the reduction of viscosity of the oils and subsequent lack of lubrication which could lead to damage and overheating of the transmissions.

As I say the crews limits were always hit first either cold fingers and feet, hunger or that bladder caption again :O

[SASless]

Lowest temp for me....having done three years in Alaska.....I now set the limit at about 60 F with the aircon running.

We routinely flew in -30C and set a limit of -45C.

Even in the bush we kept the aircraft heated with portable heaters and kept the battery inside the cook house at night.

The only real change in procedures was in not shutting down away from camp for fear the rascal would not start again which would do no one any good.

[Fun Police]

SASless' response is basically what i'd say. i fly the 350 doing seismic exploration year round and we are limited by what the RFM states which is -40C. there are other considerations of course, such as if you are taking people out with you then maybe you limit should not be so extreme just in case you have mechanical problems due to the cold and the poor saps have to stay out over night. this is not so much a concern if the ground crews have road access.
our machines also stay out over night, covered, and with electrical heaters on the FCU's, oil reservoir, and in the exhaust. this is generally sufficient but with extreme cold this plus a little help from herman nelson in the morning to really get some heat onto critical components including the T/R gearbox is necessary.

i just wish that eurocopter/bell etc etc would put a provision for heated hand grips on the cyclic and collective. if skidoo can do it on their snow machines, then i cannot see why you can't have heated grips in a helicopter :ugh: .

[flyheli]

that's great info guys... thank you! I seems I have to get a snowmobile with heated grips to warm up between my flights :)

[NickLappos]

Having worked two certifications for cold qualification, I have seen that these are the places that get the most attention:

1) Servo seals - which shrink horribly when cold soaked to about -32 degrees C, and make the hydraulic system leak like a stuck pig. Especially servos around the shaft seals. When warmed back up, no problem, they seal right back up. The newer seal materials work down to about -42 degrees C, if your aircraft is fitted with them. The RFM limits are the key, of course.

2) Elastomerics, especially in the rotor head. They do not like to be stretched too far when cold soaked, but they warm up very quickly, which is the reason for warm-up times without moving the sticks on some helos.

3) Cockpit displays, especially the new liquid crystal, which stay blace until they warm up. For super cold operations, there are sometimes heaters installed to get them up to temp so you can see the gages to start.

In general, there problems are in cold soak, and are not problems when you fly a warmed up helo into temps that cold (like that silly movie 'The Day After")