Fuel Tanks - AVGAS Water Contamination - AVGAS Water Contamination

Getting airborne was easy. It was the forced landing 15 minutes later that sent the adrenaline flowing into this pilot's blood. At the first sign of rough running, carb heat seemed to work..., then I lost all power except a very faint idle. I picked out a field and made a forced landing. The next day they found ice in the fuel filter and sediment bowl; in fact, the wing tank drains were frozen and there was ice in the bottom of both tanks.

The aircraft was parked on the ramp throughout the winter. After most flights it was left with fuel tanks less than half full. On this aircraft type as on many others the fuel caps are recessed below the wing surface, leaving space for the collection of rainwater. Removal of the cap without first drying out this recess would permit water to dribble into the tank. In addition, the tank cap seals were in poor condition. The night before the incident the aircraft had been towed into a heated hangar for repairs and by flight time it was thawed out. The rapid change in temperature and exposure to the elements resulted in a build-up of water from condensation and seepage. After refuelling, the stirring action in the tanks will put the water in suspension; before draining the sumps wait a few minutes for any water to settle.

Originally Published: ASL 1/1998
Original Article: Fuel Tanks - AVGAS Water Contamination

Updating Your Global Positioning System?

The following was taken from a daily occurrence report:

In IFR conditions, a Saab 340 with 20 people on board was cleared for the approach into an MF [mandatory frequency] aerodrome. It was on short final when the FSS staff observed a Robinson RH22 inbound near the approach path to the runway.

The helo was not in radio contact with FSS and was not monitoring the MF. The Saab pilot was able to land safely and saw the helicopter on short final.

FSS staff approached the pilot of the helicopter after it landed and the pilot said [that] he had been communicating on 118.0 [MHz] (that frequency had been decommissioned [three] years previously). He said [that] this frequency was provided by his GPS equipment, but, on [being] questioned, admitted that the GPS database had not been updated for "a couple of years." He did not consult his copy of the [Canada] Flight Supplement, which was on the seat beside him, because he was "too busy." When FSS staff asked for his name, the pilot declined to give it, and said [that] "[he hoped] nothing would come of this.

Upon departure, the pilot did not file a flight plan; rather, he flew on a company flight note.

Weather at the time of the incident was 700 ft. broken [and] 2000 ft. overcast, [with] visibility 5 mi. in light rain and fog.

Communicating on the right frequency in an MF is mandatory, but it should also be too easy. Having an up-to-date Canada Flight Supplement and looking at it or getting your GPS database updated regularly may cost a few dollars, but a mid-air collision could ruin the day for a lot of people.

Originally Published: ASL 4/1997
Original Article: Updating Your Global Positioning System?

To the Letter

Re: Struck by Lightning

Dear Mr. Schonberg,

As an interested and appreciative reader of the Aviation Safety Letter, and a professional pilot for the past 12 years, I was somewhat taken aback by the tone of the article on lightning strikes in Issue 3/97. The article insinuates that many highly trained and experienced airline crew members flew aircraft near a lightning storm merely to meet a schedule. The article also suggests that the on-board weather radar would have indicated this hazard, and that the crews either didn't use the radar or didn't care about the returns. I feel that both of these comments are inaccurate at best.

As you know, weather radar indicates returns from precipitation and is consequently very useful in avoiding turbulence, windshear and hail, but gives a pilot no indication of the electrical activity in a storm cell. Recent research suggests that many lightning strikes occur when the aircraft is abeam a storm cell, rather than under or in a cell, and that they can occur at distances up to 20 NM from the edge of a storm cell. In addition, the lightning-strike potential around a storm cell is highly variable and topography-dependent; an area that is safe at one point can quickly become unsafe, and vice versa.

While I am not saying that, with hindsight, the situation could not have been better managed, I feel that it is somewhat unfair to be so quick to judge. If all aircraft avoided thunderstorms by 20 NM at all times, most western Canadian airports would be closed every afternoon in the summer months! Conventional thought and practices seem to indicate that pilots can safely circumnavigate such storms using many sources of information. That is using weather radar, stormscopes (if the aircraft is so equipped), air traffic control, and pilot weather reports, and merely by looking out the front windshield. Thus, lightning strikes are a fairly rare occurrence and, when they do occur, the design of the aircraft does what it is supposed to do and damage is usually minimal. In light of the above, to suggest that several dozen professional pilots jeopardized their passengers' safety to make a schedule is somewhat rash.

Thank you once again for the Aviation Safety Letter. I find it to be a truly useful and educational resource that is very easily understood.

Kevin Maher
Vancouver, British Columbia

More Lightning

The article states that "The lightning could easily have fried the aircraft's electronics...."

Transport category aircraft certified to the Federal Aviation Regulations in the United States, Joint Aviation Requirements in Europe, or Canadian Aviation Regulations in Canada have to meet stringent airworthiness standards for protection against the effects of lightning strikes. Two types of effects have to be considered:

1. direct effects: The aircraft must be shown to be able to withstand a direct lightning strike and not suffer structural or significant surface damage, nor shall any fuel in tanks, lines, and so on, be ignited by the strike; and
2. indirect effects: The aircraft avionics and electrical systems, including electronic controls for systems such as landing gear, flight controls, and fuel management, must be able to withstand electrical impulses induced in the aircraft wiring as a result of the electromagnetic field created by a lightning strike.

As you can see from the above, there should be no risk of the electronics being fried. The aircraft may suffer minor surface damage from the lightning-strike attachment or discharge points, and the carrier should conduct a post-strike inspection of the exterior surface to determine the extent of any damage.

A few years ago, I was in a Canadian B-737 that was struck by lightning on approach to Vancouver International Airport. After disembarking, I stood by the window at the gate and was pleased to see a mechanic walking around the aircraft, looking carefully at the radome and rear lower fuselage, including antennas. Obviously, the flight crew had reported the strike to the ground crew.

John Carr
Principal Engineer
Avionics and Electrical Systems Engineering
Aircraft Certification Branch
Transport Canada

Originally Published: ASL 4/1997
Original Article: To the Letter - Re: Struck by Lightning