AVIATION SAFETY NEWSLETTER
Thought for the month.....An aircraft on the ground is safe, but that is not what aircraft were built for.
WINTER WINGS....It wonít be long before the weather reports will be: 34010G20KT 5SM SNSH 35OVC. After sitting on the ground for weeks looking at a lot less than this, it might be tempting to get out and fire up the old air machine. Nothing wrong with that, it just requires attention to a few more details associated with flying in cold weather. One basic but often overlooked concern is fuel. If an aircraft heater is installed, itís going to use fuel. Bringing the aircraft up to operating temperatures and slower taxiing on slippery ramps and taxiways, adds 10ths to the hobbs meter which equals more fuel burned. If youíre going cross country, be sure to allow for a greater margin. While refueling, be aware that cold dry air is great for static electricity. If at all possible, be sure both the fuel truck and the aircraft are grounded. If the grounding points are covered with snow, at the very least ensure the truck and aircraft are bonded. If you detect static electricity snapping around in the fuel tank, stop fueling but do not remove the nozzle. Let it remain in contact with the filler port to help equalize the charges.
Many operating manuals contain guidance about starting in cold weather. Itís a good idea to review those procedures because they may be different from warm weather starts. Some pilots seem to think that if a little priming is good, more is better. Each year a number of airplanes are burnt down to their wheel hubs because of excessive priming. If you canít find any information from the manufacturer, check with the FBO, or an instructor familiar with that type of airplane for some specific guidance.
Some recip operators refuse to even try starting their aircraft when the temperatures drop below 20°F unless they have a preheat for the engine. Cold starts result in excessive engine wear because the cold oil has the consistency of glue and doesnít readily flow to protect all those parts rubbing up against each other. Combine cold oil with a cold soaked battery, and it might be difficult to get the engine to turn over at all. Once started, the engine should be allowed to run until normal operating temperatures are reached even if the aircraft isnít going to be flown. Water vapor trapped in fluids will condense into liquid water as the temperatures rise above freezing. If the engine is shut down before the water has a chance to "burn off", it will be trapped as a liquid in fuel and oil lines then refreeze as the temperatures cool. As the water turns to ice it expands and can crack oil lines and break oil coolers.
The aircraft must be clear of all frost, snow or ice before flying. Some people argue that itís OK to takeoff with frost on the wings as long as itís rubbed smooth. Well, the airplane will probably fly, but what are the new coefficients for lift and drag on the airfoil weíve just created? Donít know? I guess that would make us test pilots. Donít bet that what looks like loose snow on the wings will blow off during takeoff. It might be stuck, and destroy just enough lift to prevent the takeoff from happening. Itís also a good idea to remove all snow and ice from our shoes and clothing before we strap into the cockpit. Once it warms up, all that stuff is going to turn into water dripping down onto control linkages where it will refreeze later.
If things are going to warm up we need to get heat into the cabin. Doing so always raises the concern about carbon monoxide poisoning. Whether from a heat exchanger, combustion heater, or bleed air, if thereís a leak in the system exhaust can become mixed with the heated air resulting in anemic hypoxia (stomp, stomp - thatís a CFI question boys and girls). Even a small amount of CO2 entering the cockpit can quickly build-up in our system, and may result in impaired judgment and ability, loss of control and a fatal accident. Buy a new CO2 detector for the aircraft, then review what procedures you may need to employ if it shows a positive indication in flight.
Disorientation becomes a bigger factor in winter. With a covering of snow on the ground many of our normal visual clues disappear. It can make navigating more difficult, but more importantly, it can cause us to misjudge our altitude and rate of closure during landing. If thereís an operational ILS at the airport, itís probably a good idea to utilize it to ensure we have an appropriate approach angle. Approach lights and VASIs can also be very helpful in the absence of normal visual clues. Speaking of visual clues, if youíve never flown through a snow shower before you could be in for a startling surprise. As you approach one there doesnít appear to be much to it. You can usually see through them without much difficulty. However, once inside, the flakes flashing by the windscreen create quite a visual display which can become disorientating, especially at night when they are illuminated by the aircraft lights.
The final reminder is about icing. Just because the aircraft weíre flying has boots and prop deice, doesnít mean itís certified for flight into known icing. Aircraft that are certified into known icing are probably not certified for more than moderate. No aircraft is certified into freezing rain. Even in severe icing, the amount of weight that we pick-up probably wonít be that significant, but the effect on lift and drag is. In our basic GA airplane, if we inadvertently get into icing, and see it building on the leading edge of the wings, it is a sure thing that it is already accumulated on the horizontal stabilizer. A stabilizer contaminated with ice will stall at a much higher airspeed than normal so we want to use minimal or no flaps, keep the airspeed higher, and fly the airplane onto the runway.
We can avoid all these cold weather concerns by simply not taking the aircraft into the air. But, thatís not what aircraft were built for.
Cape Girardeau Airport
Cape Pilots Club Building
Operations at Towered Airports
7 to 9pm.
St. James, MO
Operations at Towered Airports and LAHSO
AOPA Air Safety Foundation
More of Never Again
Balloon Instructor Refresher Clinic
Super Safety Seminar 25th Anniversary Program featuring Phil Boyer and Rod Machado
Boeing Building 33, McDonnell and Lindbergh Blvds
8am to 3pm
Feb. 19 & 20
FIRC - Greater St. Louis Flight Instructors Renewal Clinic
St Louis University
LET'S NOT MEET BY ACCIDENT
FRED P. HARMS
Safety Program Manager
1-800-322-8876 x 4835