Ice and snow removal?!

[Crossunder]

Just wanted to know if there are any publications out there regarding airfoil and airframe icing, and the effects of snow and ice on the aircraft (not just a PPL handbook which states that ice / snow is dangerous; end of discussion)?!
Every now and then I fly with captains who are hysterical about even the slightest evidence of rime or ice, and will spend thousands of dollars on (what I would consider) needless de-icing. Then there are those who never seem to de-ice no matter what the flying conditions are like. I'd really like to slam a NASA research paper on the table and say "Aha! Look at this you imbesile" (or something to that effect ;-)).

Help?

[maxalt]

Dear Crossunder, when your crusty old captain insists on a 'clean aircraft' don't be so dismissive. Certainly the modern rules allow 'X' ammount of 'thin rime ice' on certain parts of the airframe, but ask yourself this....if there's an allowable ammount of 'rime' on the top of the fuselage (a non aerodynamic surface....whats the problem) then are you sure the top of the wing (the bit you can't easily see on a walkaround) is not similarily contaminated?

Well...so, what if it is?

Let me tell you a story.

Many moons ago I was a young F/O converting onto a certain turboprop. We had 3 students, a training captain, and a competent F/O on board. We did two sessions of demo general handling with my fellow students that clear winters day. Finally we landed to take a break before my session. The others were all let off the aircraft before we got airborne again.

On climb out to our safe manoeuvering alt we passed through a thin layer of stratos...the first we'd seen all day. We thought nothing of it.

We set the bugs for the approach to stall. This was the third time the exercise had been done so I was familiar wiyth the routine through observation.
We were meant to get the stall warning at a good margin above actual full stall (+10 kts?) and then recover.

At Vs + 25 the aircraft started dropping a wing. I picked it up. Then the other went. The training captain told me to quit messing with the ailerons. Then we went into a full stall! No warning. No buzzer.

We fell into the cloud layer again during the recovery. Lucky it was only a hundred feet thick.

On exiting the cloud we inspected the wing leading edge from our seats. We could see a barely visible coating of rime on the LE. It was only visible because the black boots on the LE showed its presence. They would not remove it when exercised because it was too thin.

But it caused a 15kt increase in stall speed.

I always demand a CLEAN AIRCRAFT and to hell with the books or the expense.
Safety first.

[lomapaseo]

General scientific publications, are debateable and/or not very well understood by folks other than experts.

The importance of ice on airplanes and airfoils is a safety concern and as such is pubished in the flight manuals for the benefit of safe operations. This is the one document that the pilot need worry about understanding and following.

It may be that your concern is warranted if the pilot does not understand the airplane manuals and by such thinks that he is safe when he is not.

A NASA maual is not the book to start throwing in front of a pilot/

[Lu Zuckerman]

To: Crossunder

The following was taken from a commercial site on the Internet. As far as NASA generating a report the only report I could find on the Internet was generated by NACA back in 1932. Try the Internet under Ice on aircraft.

Ice on an aircraft's wing-surface can have a roughening effect, which, in turn, can change those parts of the aircraft, which generate lift. As a result, the prescribed aerodynamic safety margins, specified for the aircraft with regard to acceleration and lifting performance are either reduced or completely eliminated. In a worst case scenario, icing on the wing can even cause the aircraft to stall. Therefore ice and snow have to be removed from the aircraft surfaces by applying de-icing agents leaving their wings aerodynamically clean for take-off.

:cool: But not cool enough to form Ice.

PS: There is an outfit operating out of Mirabel Airport, Quebec that uses compressed air to remove snow and accumulated Ice. It does not get everything off the aircraft but it saves thousands of dollars in Glycol usage.

[RatherBeFlying]

After spending two hours carefully scraping frost between the rivet lines on a C172 wing, I still had an exciting low level tour of the ravine conveniently situated at the end of the runway until I got to a speed that would give me a climb:eek:

After that it's been windshield washer fluid and squeegee until the wings shine.

That said some a/c such as the A310 are certified for take off with frost over the wing tanks, which can happen if you land with cold soaked fuel. Canadian regulations require perfectly clean wings in any case.

[lomapaseo]

That said some a/c such as the A310 are certified for take off with frost over the wing tanks, which can happen if you land with cold soaked fuel. Canadian regulations require perfectly clean wings in any case.

Interesting!, but could you elaborate. Did you really mean "over" in that the ice was on top of the wing, or was the ice on the underside of the wing where it would be the closest to the liquid inside.

Also, what certification permits this? was it the design of the aircraft or the operation of the aircraft?

[pigboat]

RbF, shouldn't that read "on the underside of the wing?" Gulfstream and Hawker Siddley permit this.

[RatherBeFlying]

pb and lmp, when I was looking after Wardair's computer systems, I observed frost over the wing tanks from my SLF seat and later sent a query about that to the CP. His reply was that the A310 was certified for that and from what I observed, the takeoff performance did not seem degraded.

As you have both pointed out, frost can be on the underside as well, but I did not do the walkaround;)

Upper surface airfoil frost likely has more serious performance implications than lower surface and distance from leading edge would also come into play. I saw maybe 10-20 square feet of frosted wing surface, a miniscule fraction of the A310 wing area.

If you see frost on a wing tank, it may well be on the other side too -- a lesson for all of us.

[lomapaseo]

Well RBF, you've answer at least to the source.

However, for any others, I would certainly like to know more.

I am aware of the general permission to accept frost due to condensation associated with cold fuel at the bottom of tanks on the undersides of wings.

However I am not aware of such permission extending to the upper sides of wings where a good deal lower overall outside air temperature is needed (fuel liquid temperature is not as effective with substantial air-gaps) and hence a much larger contaminated layer is likely.

Lacking any further comments, I might chalk this up to hear-say.

[john_tullamarine]

Boeing published some years ago after a research program .. surface irregularities in the region of the LED as small as sandpaper had significant adverse effects on CL .... not good ...

When I eventually track down the paper I will put it on the TL sticky thread.

[RatherBeFlying]

lmp, on the ground the area of the upper surface of a fuel tank in contact with fuel will depend on fuel volume and tank geometry.

The upper surface of a wing fuel tank in most wing profiles is normally lower towards the rear. At a threshold fuel volume, the upper tank surface will be in contact with the fuel. As fuel quantity increases the upper surface contact point will move forward.

[safetypee]

In aviation there are three types of ice.
Good Ice, Bad Ice and Hazardous Ice.
Good Ice is found in the galley.

If you don’t have a galley refer to your crusty old captain.

Also see AC 120-58 Pilot Guide for Large Aircraft De-Icing
http://www2.faa.gov/index.cfm/677/7728B246-9A06-4C76-B8A963F429C5403A

[Transition Layer]

All this talk of ice makes a 45C day and a QNH of 995 sound like very appealing flying conditions!!!

[dolly737]

maxalt, safetypee & john_tullamarine have said it all.

There is another catch: You might get away a hundred times with a “little” ice, probably not even noticing anything during your flight. But when it comes to situations requiring max performance i.e. an engine failure during takeoff, that trace of ice on your wings (and fuselage) can erode the life-saving bit of climb capability you would otherwise have had.

happy landings

[4Screwaircrew]

Regardless of the price deiceing is cheaper than crashing.

[Crossunder]

Maxalt & LuZuck:

Point taken ;-) Of course I never take off with loads of wet snow or ice/rime on the wings. What I had in mind was the other day when it was around 14-15 below freezing and the snow was very dry / loose. The wind was about 11-13kt, so the only precipitation sticking to the aircraft was that which hit the heated windshield and melted. If we'd applied a layer of sticky fluid to the airfoil; wouldn't this reduce Clmax more than if we let the snow blow off? (Our SOP requires all V-speeds to be raised by 10kt when de-/anti-icing is performed). If there is any doubt, I always insist on deicing, but in this particular case, both the captain and ground personnel inspected the wings and we decided to go without deicing.

Anyways, I must admit I never really thought traces of rime could f**** up the a/c performance that bad (as Maxalt describes), but from now on, this F/O will start deicing a lot more often.

Merry Xmas airmen!

[rnobson]

Any idea how many pilots (lucky enuf to have made it out alive) have said with a mystifide look on their mugs " funny I have taken off b4 with much more frost that that on the plane !!"

[lomapaseo]

Anyways, I must admit I never really thought traces of rime could f**** up the a/c performance that bad (as Maxalt describes), but from now on, this F/O will start deicing a lot more often.

Depends on what your leading edge looks like. Fixed leading edges, ala DC9-10 vs extended slats, are much more sensitive to airflow separation (sandpaper, bug splat effects} than the more common extendable slats on today's big passenger jets.

As I said earlier, follow your operating manual for the equipment that your flying, for many of the reasons stated in this thread, and forget about the ole wifs tales that you might pick up on forums.

[Lu Zuckerman]

PS: There is an outfit operating out of Mirabel Airport, Quebec that uses compressed air to remove snow and accumulated Ice. It does not get everything off the aircraft but it saves thousands of dollars in Glycol usage.

I contacted the snow removal company in Mirabel and they told me that their first contract was with Air Canada (20 aircraft) and in one year the airline saved 8 million dollars (Canadian) in deicing costs.

:D

[Captain Stable]

Not much holdover time, though... :(

[sky9]

Lu
It's non-polluting as well. Can only improve the environment.

[sharpshot]

Whilst not in full agreement with L337's description of events that led to the accident to N90AG at EGBB last January, the AAIB final report will no doubt answer the key question posed at the start of this thread.

Please do read it carefully.

The first knowledge I have of accidents caused through a lack of de-icing goes back to the 1930's when a flight of military aircraft took-off from a field in Scotland. All came back to earth with a bump! It was a relatively new experience in those days to discover the effect of ice and frost on even basic aerofoils, let alone super critical wings.

Why is it we are even still asking the question - do we never learn!

[L337]

Whilst not in full agreement with L337's description of events

Very third hand description it was. But reliable source! So I hope not too far from the truth.

L337

[Firestorm]

NASA did quite alot of research after the ATR turned over a few years ago as a result of icing. Some of the tests were done on an ATR and some on a Twin Otter: several papers were produced as a result. I don't know where you would get copies, but I saw them at Flight Safety Canada (Toronto): might be a starting point for you. There is also a pink AIC: check your AIP in your ops room, or where ever your company keeps it. In essence it says if in doubt, deice, and be very careful about hold over times, and if you're still in doubt, deice again. It is illegal to take off with contamination on the lift surfaces.

That said, and this was a special situation, in the Sahara in winter there is often a frost at night. The temperatures rise quite quickly as soon as the sun comes up and melts the frost off the wings almost instantaneously. Ground temperatures could be -2 or -3, but temperatures at 50' would be in the order of +10 or so, and there was no deicing on hand anyway. We were allowed by company rules to depart with frost on the wings, but not ice.

[maxalt]

I see Airbus have just published a bulletin relating the dangers of contamination on A321 wing surfaces and referring to two incidents of near loss of control in flight caused by ice.

Procedure recommended...use F3 for landing and VLS + 10 minimum.

[sharpshot]

L337
Think you will read about the effect of APU exhaust and its role in the particular ambient conditions on that day; not the morning sunlight.

I think one of your other comments may have been speculative.
Enough said.