The Pilot in Command’s Catch 22

When trying to keep his aircraft and its engines free of ice

Catch number 1: Snow before Take-off

Foto: Adam Tow,

After de-icing, done by trucks or at a centralized station, the Pilot in Command (PIC) has a ”Hold Over Time” (HOT) to observe before a new de-icing is needed. In heavy snow a new de-icing is required typically every 5-10 minutes.

This requires either taxiing back to the ramp, or holding back all trafic, while a de-icing truck arrives at the T/O position. Smart airports have one or two de-icing truck on standby at the take off position.

Catch number 2: ” Engine run-ups ” not done, in time

Most airlines introduced a SHALL DO to the periodic engine run-up procedure,
(some major airlines still leave it up to the captain, with a SHOULD DO) but the ice might still build up to a dangerous thickness if the 5 or 10 minuts intervals are not respected.

Poor Braking Action (B/A) on slippery taxi ways can stop the captain from doing run-ups. Other aircraft too close behind can also make it impossible.

So! If the captain does not do the run-ups in due time, they can actually destroy the engines and may not be performed. This leaves the captain with two options: Either taxi back to the ramp at idle power, shut down and have the engines hands-on inspected and maybe de-iced by a hot air gun before starting up again. Or send for a mechanic and a truck with a hot air gun and have the procedure done at the take off position.

Braathens Airline (Norwegian) used the mechanic with a hot air gun at a place near the T/O position, but without holding up other aircraft ready for take off. This flexible procedure was implemented after the hard earned lessons of December 14th 1998 at Oslo airport Gardermoen. This only lasted until Braathens was sold to SAS in 2002. Nowadays SAS/Braathens just give up taking off until weather conditions improve. This seems like a strangely defensive attitude and a waste of the passengers’ valuable time as well as the 32 billion Nkr. which was the prize of this misplaced airport. (Click here to read the story of Gardermoen).

Earlier, these unavoidable delays could cause inconvenience or connection problems and even crew change. Now, the captain is furthermore faced with the new European Union rules on monetary compensation to passengers for cancelled flights and lengthy delays. In 2005 British Airways got into a diplomatic crisis with the American authorities, the Federal Aviation Administration (FAA). This happened because a British Airways Boeing 747 flew from Los Angeles to Heathrow, London on just three out of four engines. The only reason that this attempt to avoid the new rules for monetary compensation was exposed was that the plane was forced to make an emergency landing in Manchester due to a lack of fuel. Therefore the flight became the subject of the authorities’ attention. Investigations revealed that the same plane made a flight from Singapore to London only six days later – again most of the way only on three engines.

These dilemmas were examined by Cranfield University student Javid Karim in 1995:
An Investigation Of Aircraft Accidents And Incidents Attributed To Icing, And Cold Weather Operations.

His investigation covered app. 50 of the world’s major airlines and the results indicated:
A general lack of crew awareness and training concerning winter operations.
Some pilots have admitted to taking off with expired periods / hold-over times, which is extremely hazardous

Finnair is the only airline to earn a superior rating, when confronted with winter operations.

Catch number 3: ”Landing with excess cold fuel”

This happens when flying time exceeds 3 hours, or extra fuel is carried due to bad weather, or  there is no fuel available at the destination, or because fuel is too expensive at the destination.

Foto: Adam Tow,

When parking with an upper wing surface temperature of – 30 degree’s C. any rain, even in warm weather, will form crystal-clear ice on the wings right in front of the tail mounted engines. This is the case for some of the world’s most popular passenger jets such as the DC-9, the Boeing 727, and the MD-80.

This is what happened on December 26th 1991, when a SAS MD-80 returned from Zurich to Stockholm, where a fuel-strike was threatening, with 5-6 tons of extra fuel. This was enough for the first flight the next day. The plane was parked outside in rainy weather which later turned into snow.

The next day Captain Stefan Rasmussen flew this MD-80 for four minutes, before skillfully crash landing it on a rocky field with both engines destroyed by ice from the wings.

On December 26th 1991 all SAS aircraft were landing in Stockholm with fuel for one extra hour, and at least one MD-80, besides Capt. Rasmussen’s, had its engines damaged/destroyed by ice. The first flight to Oslo had had an engine over-heat warning, but landed safely at Fornebu Airport. The warning was cancelled when the captain slightly reduced thrust. This was noted in the aircraft log. Due to that warning the plane was extraordinarily inspected in the dark of night, and released for flight back to Stockholm. Here mechanics found one engine damaged and one almost destroyed, in daylight the damage was obvious.

Finnair came up with a procedure to avoid wing-ice, by spraying de-icing glycol from a rucksack sprayer on the cold corner of the filled fuel tanks upper surface (click here), immediately after landing. However, it is difficult to explain this procedure on a nice summerday at a Mediterranean airport, when no other country or airline is using it – to the best of my knowledge. This is particularly where the problem can be neglected by the captain. The only way for the captain to avoid this problem is if he is so lucky that there is in fact a Finnair mechanic stationed at the airport, who has the rucksack sprayer and knows the procedure. Otherwise the captain will simply have to wait until the ice melts, or use hot water to remove it.

Catch number 4: ” High altitude airframe icing ”

Tiny water droplets can remain liquid at temperatures down to -60 degrees C., and pilots must know that they have to leave their flight level immediatly after detecting the severe icing condition. On December 21st 2002 a Taiwanese ATR-72 forgot to do this at flight level 180 where the temperature was -9 degrees C. The captain failed to disengage the auto pilot, and therefore the auto pilot continued to attempt trimming the plane to maintain altitude and speed while ice was building up on the plane. This resulted in the auto pilot eventually disconnecting. By then the plane was so out of trim and so covered with ice that the captain was unable to regain control. The plane went into a spin and crashed. All on board this freigther died. This in spite of the fact that the de-icing system was in fact turned on.

As a consequence the Taiwanise Aviation Safety Council urged all airlines to review their icing training.

So, my dear fellow pilots:
”Aircraft are ice-sensitive, at any temperature.”

Since winter problems are the same for all airlines, manufacturers, and authorities, they should all agree on uniform world-wide procedures, and Flight Data Monitoring (FDM) must be used, as it has been in SAS for 30 years, to check approach and landing flying behaviours. SAS has by the way exported the computer program used for this purpose world wide. FDM is also known as Flight Operations Quality Assurance (FOQA).

This way we can ensure that all necessary run-up procedures are done, and hold-over times are kept because the airline industry should not have to live with these dilemmas.

Oluf Husted
April 13th 2005