Icing thoughts

[fernytickles]

Does anyone know where I can find accurate figures for the increase in stall speed caused by ice accumulation on the leading edges? Or does anyone know these figures.

I don't know if the figures are the same regardless of type, but I am flying a small twin, which, of course, on the whole, flies right in the most icy levels. I've landed with ice still on the leading edge and have used a scraper to remove it before taking off again, but it was making me think about how much the accumulation affects the stall speed.

Thank you :)

[Old Smokey]

Sorry to spoli your day fernytickles, but icing is a real 'wild card', no two icing encounters are the same, and there's no generic formula for calculating stall speed increase.

The affects (as I'm sure you know) can vary from minor, to extreme, with all possible combinations in between.

Regards,

Old Smokey

[fernytickles]

Old Smokey,

Thanks for such a quick response. I guessed that might be the case.

I know we just added a generic 10 kts to the final approach speed when I was flying larger planes. I have been thinking about what if I had to go around, now that I have seen the accumulation of ice that I have knocked off the leading edges after I land. I suppose I'll just proceed with lots of caution.

The plane does have boots, and they do have some effect, but nothing to get too excited about.....

[RatherBeFlying]

The statistics show a significant proportion of icing accidents are stalls on approach after getting the ice laden a/c to an airport.

A looooong runway and lots of extra knots might help with an iced up piston twin or single.

[Tankengine]

Fly around in a light twin too long in icing conditions and you won't need to worry about it!:E

[fernytickles]

Ratherbeflying

Interesting point, I guess when I think about icing accident reports that come to mind, such as the King Air in Minnesota, that crashed during the approach. Maybe I'll add a good 25+kts to the approach speed, just to be on the safe side...... And stay clear of ice as much as possible...

[john_tullamarine]

leading edge ice ? around about the worst sort of place, I'd opine ... have a dig through the Boeing mags for the article on icing which looks at the (dreadful) effects of (even just) sandpaper roughness levels due to ice with the LEDs on the jets .... a bit different on criticality with a GA slabwing .. but the principle still applies ... no ice = good ice.

[Piltdown Man]

It all depends on the wing section. In the past, I have flown many different sorts of gliders and each reacted to ice differently. The older types with non-laminar sections generally appeared not to be bothered by ice (maybe an increase in 10% or so with a thickish layer of ice) but some newer types (DG500 for instance) would fall out of the air with one or two bugs on the leading edge. And if you made cloud climb through the icing level you might find that you would have to add 50% on to your normal flying speeds to keep the damn thing flying with only just a trace of ice on the leading edge. Therefore only the safe way to fly in icing conditions without ice protection is to use the "Calendar Method" ie. wait untill you get a month with no ice (or, I suppose, change levels).

[ssg]

As someone who flies around the Pacific NW US, used to in singles, light twins, tprops, now jets, I think I can chime in on this one.

Without boring you with icing stories, another aviation tale, I will simply make some points.

- Judging the amount of ice in inches, has always been a kinda joke, a best guess.
- Ice affects by decreasing lift and increasing drag, a double whamjy.
- As a wing accumulates ice, you become a test pilot to as far as what you can carry safely to the ground.
- Recent NASA studies, which I think are a joke, direct the pilot to working the boots every time he sees ice, based on new boot technology, not taking into account that if your really flying in this stuff at say 12k feet, your probably flying an old 70-80s aircraft, old tech, old boots. While they did expand on tail plane icing, there is not alot a pilot can do about it. I've moved passenger out of the back and over the wing, to get another 500ft/m because of tail plane icing, its serious, and do that was the difference between going home, or getting over some hills.

Tips:

Keep your speed up, ice can't stick if your moving fast
Keep the boots clean and working
Spray with table polish, ICG, WD40 before each flight, it works
Get out of ice ASAP, but 180 turns are stupid
Watch your temp guage and fly where it's either to warm or too cold, and stay out of the buildups, tops, and windward side of mtns due to upslope icing, get above them first if possible
Bring some 02 to get to that 15-16k alt to get above the freezing level if only for a while.
Watch your AS ind. If you have ice, and lose 20 kts max on cruise, it will be worse with reduced power on landing, think about making a change.
Wait untill you have an inch before using the boots.

Land fast, like 30kts fast, on landing if you are carrying like two inches of ice, if your heavy, it might be worse.

If your flying a Tprop or jet, this is almost all moot, so consider getitng a better job in better equip.

The good thing about all this, is flying around in light twins in real icing is a great education, in singles more so.

I hope this helped.

SSG

[Mzee]

On a critical wing, eg Challenger, any contamination, on and behind the leading edge, of anything worse than quarter mm (fine sandpaper) can reduce lift by up to 50%. That includes bugs and sand as well as ice.
Keep it clean before flight.

Be aware of supercooled droplet icing, it's dangerous stuff and a number of manufacturers have issued Flight Manual amendments as a LIMITATION that if encountered you must depart it toute suite - how do you know you're in it? big clue when side windows start to ice over!

[error_401]

Some additional information.

NASA has an icing lab whose homepage can be found here:

http://icebox.grc.nasa.gov/

From the ATR Brochure on icing: Even light ice accretion in the thickness of 1 mm (1/25 th of an inch) may reduce the CL (coefficient of lift) by 0.5. From an aerodynamic side this is half the lift. So keeping up the speeds is the first thing to do.

In the ATR turboprop (22 tons MTOM) this means up to around +40 kt for flap retraction speeds and up to +18 kt on APCH speeds with working de-icing eqipment. And the boots on the ATR are doing a terrific job.

SSG's considerations - nothing to add.

error

[aztruck]

Ferny .....you got the job!! Give the Chang a pat on the nose and Fuddy duddy a quick cuddle. Do they deice /anti ice over there or are they too tight? Are you single crew on the beast? Ice, single crew, night... all sounds very intrepid. Best of luck and give him indoors my regards. Happy Christmas. Catch up in the new year. Give us a PM if you fancy.

[arismount]

The Minnesota "accident" had little to do with icing conditions, though they were present.

The PIC allowed the speed to decrease when leveling off from a dive-and-dash nonprecision approach. The other pilot didn't catch it.

Totally the result of poor training and inexperience on the part of the second pilot, unfitness on the part of the PIC. Read the report and draw your own conclusions; I did and those are mine.

For you new men reading this, I highly recommend not removing your hands from the power levers when doing a dive-and-dash; in this way...hopefully...you are more apt to remember to bring in the power when leveling off.

This is an extremely high-workload period and there is many a pilot who has forgotten to power back up until the speed gets very slow. Most of them are able to recover and learn a lesson; the Minnesota mishap pilot was not and is dead.

[Dream Land]

King Air in Minnesota, that crashed during the approach.

Just read an article in Pro Pilot about that accident, they seem to think the FO was flying (700 hrs TT). Also, the King Air will handle the worst of weather without a problem.

D.L.:ok: