Deicing boots - when to use them

[Baseturn]

My company advocate using the boots when sufficient ice has built on the leading edge as premature use can lead to bridging. Our airline operates TP aircraft with spanwise boots. I read with great interest the FAA's reccomendation that boots should be activated at first sign of ice and would like to change the standard practice currently adopted by many airlines.



I open this up to anyone with experiene with TP's and invite your view:eek:

Thank you

[smallfry]

What does the aircraft AFM tell you to do?

I used to fly pistons and turboprops where the philosophy is to wait until you have a build up, then break the build up off with the boots. I am now flying a type that you run the boots all the time in icing conditions, as you must get off any traces of ice, and 'bridging is not possible'. I was dubious at first, but the manuals very clearly advise us to do this.
It is all up to the manufacturers and the certification of the aircraft.

[GotTheTshirt]

Generally boots are considered De-icing and hot air is Anti-icing:)

[Hoover Pilot]

Fokker 50 manual says boots to light upon ice detection - then increase to heavy if in opinion of pilot rate of ice build up is suffucient between boot cycles.

One of the pitfalls of waiting is that ice can build up on tail - but this is not visible to pilots and can lead to problems. I follow the manual and have never experienced bridging so far....

HP

[Strepsils]

The "wait for 1/2" or so of ice" philosophy to prevent bridging is fine on light aircraft, but most TP's will have a high pressure feed to run the boots which combats the bridging problem.

Check with your flight ops or even email the aircraft manufacturer.

[Baseturn]

thanks guys

Our AFM clearly states that the pilot must operate the boots when 1/2 inch ice is visible and thats of course what we do, however it is interesting to note other operaters recomendations on what are similar aircraft.

I find icing a very interseting subject and one that is very popular with the AAIB! it is very interesting to see that there are differing opinions and operations of similar or infact identical systems for something which has a fundemental purpose.

The aircraft we operate has a very clean relativley thin camber with high wing loading which should keep it mostly free from icing comapred to slower higher lift aerofoils but this of course means it is perhaps less accepting of ice contamination.

Thanks again so far

[rigpiggy]

Everything i've flown up to the 748, uses between 16-20 psi for boot inflation, anymore would increase the chance of failure. The lighter stuff may not have the same flow available due to the use of Vacuum pump vs. bleed air, but generally runs about the same pressure

[Jet_A_Knight]

Those things (boots) just give you a false sense of security.:{

Blow the ice off asap, then get out of the icing conditions.

Like hoover pilot said, you can't see what is going on at the tailplane - and no one wants any tailplane initiated adventures going on inadvertently or otherwise.

They just buy you some time - they're not a panacea.

[alf5071h]

Several years ago the FAA ‘over reacted’ to an icing accident and ‘mandated’ immediate use of de-icing boots in icing conditions without consultation. Some manufacturers followed the FAA requirements (no legal liability ?) others retested or submitted test results to support their recommended procedures.
There have been arguments both for and against ice-bridging; if it happens you shouldn’t be in those conditions, but how do you judge that before the event; the first thought when entering icing conditions is how to get out.
De-icing boot design, loction, and aircraft type have their own icing characteristics; horizontal ribs or vertical ribs have different effectiveness, similarly for pressure, cyclic times, and areas covered. Thus always follow the manufacturer’s instructions.
Also see A Pilots guide to icing. (http://aircrafticing.grc.nasa.gov/courses.html)

[Piltdown Man]

Whilst the boots may get rid of ice that has accumulated, a change in level of even 2,000', plus or minus, will often result in a level where the rate of ice accumulation is no longer a problem (assuming it was before). Prevention is always better than a cure.

[On speed on profile]

Before getting airborne, and knowing icing conditions are likely, what do you do. Here is my example.

I canned a flight (C400 series air taxi certified into moderate icing) flight because of the wx forecast. It was basically Strato Cu from 400' AGL to 12,000 AGL. With 0 degree isotherm at 400'. The weather chart was showing moderate icing when in cloud and because I wasnt oxygen equipped, I canned it as I knew I would never be out of the cloud and therefore the icing. The trip was only 35 - 40 mins but I had to use Cessna 400 boots! Not the best and most reliable boots in my opinion! I had picked up considerable ice accretions in the previous two days and because of this had tried both techniques, 1/2 inch and straight away! Both with limited success.

My questions to you people. Would you do the same, why or why not?

At what point would you keep the aircraft in the hangar.

Cheers,

OSOP


P.S. Pilot man down, I think NASA states a change in level of 3000 feet is more likely to do the job. Havent had the chance to test that theory yet? Please correct me if Im wrong, you obviously have been there done that flying the Fk50.

[SlowAndSilly]

Hi!

I fly with captains who do both, and believe me:

Leaving them on in icing conditions works best. Everytime!

brgds

[AtoBsafely]

In my experience it never hurts to put the boots on right away, but if all you have is light rime they probably won't do much.
In slightly heavier icing the ice breaks off more cleanly if left to build up A LITTLE, but it will not build up much if the boots are running. I have NEVER seen any bridging build up. In my experience, the FAA policy is safe and foolproof.
In any moderate or worse icing an altitude change is good, and 2000' makes a difference. 4000' may be better.
OJ