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I am working on a plan to minimize frost on an unhangared EMS helicopter. I am proposing to run the aircraft up for 5-6 minutes when OAT drops to 4 deg C, and repeat every couple hours until the temp drops below -4. We don't get a heavy frost, so if we could prevent accumulation the aircraft would be able to respond more quickly.

How do others handle this issue?

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I don't have any idea, but I bet your relief would like to come up with another plan than getting up to run the helicopter every two hours! I don't even know if it would work. On the more serious side, putting a cycle on the helicopter to frost prevention could be expensive. The only thing I can think of is to cover them.

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Covering, hangaring are delays we're trying to avoid.

Cycles are well spent if they increase business and eliminate hazards.

This is a job, sleep* when you don't have anything productive to do.

We rotate night shifts, nobody bears unfair burden.

 

*At one time CAMTS proposed eliminating pilot beds. I thought that was the stupidest idea I ever heard, depriving a pilot of a good sleep when required. I'm starting to understand the issue CAMTS was addressing- pilots coming to work expecting to sleep...

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I'm with the camp that would recommend covering. It doesn't need to be covered all the time, only when the conditions warrant as you described. The amount of time to remove blade and windscreen coverings is minimal when compared to the inefficiency of run ups for clearing frost. On a run up will the defrost be effective enough to clear the windshield? I doubt it. With a heavy frost potential damage from blade slinging? Sometimes simple is best.

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Wally,

 

Hangaring is always the preferred method, but of course those of us on top of a hospital don't always have the luxury of running for the hangar because of frost.

 

Blade covers are fine if used before any moisture parks itself on the blade, but in my opinion are a nusiance - they take about 20 minutes to install on a Bell 407 and a bit less to remove.

 

If only light frost is on the blades, then you are most likely authorized by your GOM to start and runup the rotors to eliminate the frost, but you will have to shutdown in order to visually check the blades clear. This will slow you down a few minutes but is definitely faster than having to remove blade covers.

 

If hangaring is out of the question, probably the most effective method (if allowed by your GOM) is to use a type 1 deicing fluid. Simply place a thin layer on your blades and you will most likely experience hours of frost free time.

 

Of course, every situation is different. My company allows pilots to turn up the aircraft to eliminate frost buildup but trying to prevent such starts in the first place is usually best.

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With my limited experience with such conditions, I’d say blade sleeves and a windscreen cover would be the way to go. If a delayed launch time is a concern, then the issue is no longer about frost….. It’s about launch times….. In short, do you launch with a chance of frost or take an extra few minutes and launch without any frost at all?

 

Is a hangar even available? If so, are you on a dolly? Opening the hangar doors and pulling the machine out on the dolly takes very little time. However, you’d be talking about the same amount of time to pull covers off the machine although if it’s that cold, I’d prefer a hangar instead of climbing into a fridge at O-dark…..

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I use blade covers installed prior to moisture/frost building on blades. 15 min to install, 5 to remove on an A109E. A heater in the cabin will keep windows from frosting up.

 

Edit: heater also makes water, which rolls down and makes icicles :-/

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  • 2 weeks later...

The idea to run the helicopter every few hours is bouncing around on my end of the EMS pond. We're not in the coldest or wettest of environments so it's a somewhat rare occurrence but buried deep down in our stack of legacy memo's it says to run the helicopter every 4 hours if below temp X and every 2 hours if below temp Y.

 

From what I've seen, it's unanimously not followed.

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  • 11 months later...

I'd be wanting to get inlet, blade and windshield covers at least. Not because of frost. Our hawks sit outside and regularly get super frosty and we don't bother shutting down to make sure that the frost is gone. Air friction takes care of that quick. I'd be more concerned about freezing precip creating a thin layer on the bird, which could FOD out the engine if it breaks up in chunks. Or hail.

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  • 4 years later...
On 2/10/2015 at 9:56 PM, helonorth said:

I don't have any idea, but I bet your relief would like to come up with another plan than getting up to run the helicopter every two hours! I don't even know if it would work. On the more serious side, putting a cycle on the helicopter to frost prevention could be expensive. The only thing I can think of is to cover them.

That's true!

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