Frost Kills (to state the obvious)

[Dog]

No; serious question. Is the airflow on the high pressure side effected to the same degree that the airflow on the low pressure side is? I'm thinking that it's probably not.

[Hedley]

I think I've just figured out another topic that can be used to fill the additional 40 hours of ground school training required for the commercial licence as of 1 dec 06.

[niss]

I would think that if the boundry layer on the high pressure side of the airfoil were contaminated it would be too turbulent for the low pressure side to catch up and reconnect with the original airmass, theirfor the low side would become turbulent as well....

Thats just based on my limited understanding, please dispute it if im wrong.

[Hedley]

Excuse me, I'm going to go outside and cry for a while.

[niss]

Fine be that way.....just based on my limited understanding....thats my theory, please correct it for me so I know how it actually works.

Educate Hedley, don't degrade....

[Dog]

Sorry Hedly,
But please come down off your soap box and enlighten us with your obviously superior knowledge of aerodynamics.

I was under the impression that part of the reason for the performance losses caused by frost was the early separation of the laminar flow on the top of the wing. I was simply wondering out loud if problem exists to the same degree on the bottom of the wing were the relative airflow is actually helping keep the airflow attached. I know there is still a drag penalty.

[niss]

HUH?!?! Is that not what I said?

[the_professor]

Wrapped it around [snip] and worked it back and forth like you would polish a shaft.

Polishing the shaft for an hour and a half on company time.... tsk tsk

[invertedattitude]

Interesting, from the report:

FAR Part 135.227: "No pilot may takeoff an aircraft that has frost, or snow adhering to any rotor blade, propeller, windshield, wing, stabilizing or control surface, to a powerplant installation, or to an airspeed, altimeter, rate of climb, or flight attitude instrument system, unless under the following conditions: (1) Takeoffs may be made with frost adhering to the wings, or stabilizing or control surfaces, if the frost has been polished to make it smooth. (2) Takeoffs may be made with frost under the wing in the area of the fuel tanks if authorized by the Administrator."

Without digging it out, the Canadian rules differ somewhat.

A lot of airplanes now are not certified to fly with frost even on the fuselage of any depth.

BTA's E145s for example must have any and all frost removed from the fuselage as well as critical surfaces.

[CD]

602.11 - Aircraft Icing

As to the FAA regulations:

SAFO 06014 - Polished Frost
Flight Safety Foundation: Regulations Allowing "Polished Frost" on Aircraft During Takeoff Must Be Eliminated

[Axial Flow]

(7) Before an aircraft is de-iced or anti-iced, the pilot-in-command of the aircraft shall ensure that the crew members and passengers are informed of the decision to do so.

What is the deal with that last rule from the CARS ? I mean does it let everybody stop crapping their pants knowing you aren't flying with Captain Kavourkian who is gonna take off with the unclean wing ?

[CD]

What is the deal with that last rule from the CARS ?

If you have the opportunity, have a read through the Final Report of the Commission of Inquiry into the Air Ontario Crash at Dryden, Ontario. You will find the answer there...

By the way, here is a speech that Justice Moshansky gave a few years ago:

Address by the Honourable Virgil P. Moshansky, C.M. Q.C. - October 22, 2005

[Bede]

The RJ is certified to take off with upto 1/16 of ice on the underside of the wing or 1/8 inch frost.

I believe frost covering the entire top section of a wing is far more detrimental to flight than ice on the leading edge. Frost causes an increase in the thickness of the boundry layer. This results in less laminar flow. Laminar flow on the underside of the wing is not nearly as important.

Has anyone seen any videos of certification for ice testing. Engineers will strap 2x4's with jagged edges on the leading edge. Plane still flies.

[sky's the limit]

According to you guys, I'm dead 40 times over already....

STL

[planett]

Frost on the bottom of the wing has an effect. How much? I don't know. I do know that a number of aircraft have information in their Flight Manuals allowing frost on the bottom of the wing if it is limited by certain boundaries.

I have read the supplement and operated in accordance with it many times, but only on aircraft where it is permitted. I never noticed any performance or control issues. One time I foolishly ignored a few snowflakes which stuck to some fuel on the top of one wing. An otherwise clean wing. The snowflakes covered an area of 1.5 sq ft. The control issues are still clear as day in my mind. It was like having aileron trim cranked full left for the first minute of flight. It wasn't snowing either, I think it just blew off a roof of a nearby building after fuelling. Be careful out there.

[CD]

Federal Register: May 8, 2008 (Volume 73, Number 90)]
Federal Aviation Administration
14 CFR Parts 91, 125, and 135

Removal of Regulations Allowing for Polished Frost on Wings of Airplanes

SUMMARY: The FAA is proposing to remove provisions in its regulations that allow for operations with "polished frost" (i.e., frost polished to make it smooth) on the wings of airplanes operated under parts 125, 135, and certain airplanes operated under part 91. The rule would increase safety by not allowing operations with polished frost, which the FAA has determined increases the risk of unsafe flight.

DATES: Send your comments on or before August 6, 2008.

Complete text of proposed rulemaking here...

This is the full text of the link (both work for me):
http://edocket.access.gpo.gov/2008/E8-10246.htm

[xsbank]

Can you please re-post the link? I can't get it to work (the original post, the AAIB one).

[Liquid Charlie]

I know boeing allows frost on the underside of the wing - no I can't remember how much that's what manuals are for -

Another point -- splitting hairs here but the captain in the dryden incident had never seen the inside of a hawker -- but he had thousands of hours in cv's - yes it did contribute to the accident -

to depart with contaminated wings - to take off under such conditions has always been against air regulations -- I know first hand -- but that was a TC inspector just being to chicken shit to ask what was going on -- all he did was create paperwork for himself -- haha --

"roping" -- sweeping and anything that you do "in the field" does not remove the frost -- just knocks it down so the wing will fly until friction wears it off -- doesn't work for "critical wings" -- it all boils down to know your airplane and understand applying deicing fluids -- that can create more problems than it fixes in certain conditions with primitive application equipment.

[rigpiggy]

Read your FOM, I believe you're allowed 1/8 inch on the underside in vicinity of the fuel tanks

Slightly off topic... I've been flying some Beech 1900Cs lately with different serial numbers. We have one UC number machine with the later fuel system in it that is particularly susceptible to frost forming under the wing due to the cold fuel from flights at altitude. We're all used to discussing the effect of frost on top of the wing; how much effect does the frost on the bottom of an airfoil effect lift?

[Dog]

Correct. Same on some other types as well.

[CD]

FAA Says No More 'Polished Frost' on Private Jet Wings

U.S. air safety regulators have decided, after almost 50 years, that it's no longer safe for private and cargo aircraft to fly with "polished frost" on their wings.

Since 1960, the Federal Aviation Administration has allowed some planes -- not commercial airliners -- to fly with ice on the wings as long as the ice was smooth. That left it up to operators to clean off the wings themselves and decide whether it was safe to go.

On May 8, the FAA proposed removing that language from its regulations. That's two years after it issued two safety alerts advising against the practice and after complaints from safety groups.

"We would have no pain whatsoever if 'polished frost' disappeared from the language," said Bruce Landsberg, executive director of the air safety foundation at the Aircraft Owners and Pilots Association in Frederick. "We absolutely recommend completely uncontaminated wings. Spray the things down and be done with it."

The regulatory action comes after several fatal crashes of business aircraft attributed to ice on the wings and an increase in the use of corporate and fractional-ownership jets in the last decade.

"It's a pretty strange rule," said James M. Burin, director of technical programs for the Flight Safety Foundation, a nonprofit international safety organization in Alexandria. "We don't know why they even allowed it."

Commercial aircraft operate under rules that call for a "clean wing" before takeoff and de-icing baths on the runaway under certain weather conditions. Passenger jets also have access to an array of sophisticated technology to respond to ice build-up on the ground and in flight, as do some private aircraft.

John Allen, deputy director of the FAA's flight standards service, said that only in the last few years has the icing issue risen to the level of "criticality" that required a change. He said the FAA had issued the two safety alerts in 2006 to get the word out quickly because rulemaking takes so long.

While the old rule said pilots could take off "with frost adhering to wings or stabilizing or control surfaces if that frost has been polished to make it smooth," the consensus now is that "you don't want polished frost, you don't want anything on the wing," Allen said.

Under the rule, pilots are not provided guidance on how to actually polish frost or reach an acceptable level of smoothness.

Thus, the FAA discovered numerous inventive, though sometimes disastrous, ways to clean ice, snow and frost off the surfaces of aircraft. Some pilots tried to polish frost by running a rope against the wing surface, brushing it off by hand or with a broom, using a paper towel, or using a credit card as a scraper.

In its proposal, the FAA said extensive research now shows that any amount of "contaminants" on the wings "increases the risk of unsafe flight."

Others have been saying that for years.

The National Transportation Safety Board has been asking the FAA since the 1990s to revise its rules on icing conditions and the certification of planes to fly in those conditions.

"We have said in past investigations that wings should be free of ice, frost or snow" said Dan Bower, chief of the NTSB's vehicle performance division. "We recommend pilots get out and feel the wings. There are small imperfections and things you may not be able to see."

A January 2002 crash in Birmingham, England, that killed two business executives and three pilots illustrated the dangers of ice on aircraft. British investigators pointed out that the plane had been flying under the FAA "polished frost" regulation and recommended that the FAA delete all reference to polished frost.

In 2004 and 2005, fatal crashes in Colorado, attributed to ice on the wings, provided impetus for the change.

In the current rulemaking, the FAA studied 11 accidents between 1982 and 2006 involving general aviation and air taxis and found that inadequate de-icing led to fatalities and injuries.

Chris Dancy, spokesman for the Aircraft Owners and Pilots Association, said most general aviation aircraft don't have equipment, such as de-icing "boots" on the wings that break up ice in flight.

Most aren't certified to fly in icy conditions. He said many pilots of private planes just wait out the weather or pay for de-icing spray.

The FAA recommends four ways to comply with the proposed rule: Use wing covers made of light fabric that keep off snow and ice, wait for the weather to warm up, park the aircraft in a heated hangar or de-ice the plane.

Public comments on the proposed deletion of the language are due Aug. 6.

Full article here...