Maintenance and Certification

Winter Operation Woes

This article was originally published in Aviation Safety Maintainer Issue 4/1992.

What differences should we be aware of with winter operations? Why do we need extra vigilance? Here are a few accidents where winter conditions were a contributing factor. I hope the results remind AMEs that, no matter how small or how large the aircraft, it is often the very simple things that cause the most serious problems.

Aircraft parked unprotected from ice and snow
Aircraft parked unprotected from ice and snow as shown above, require inspection for possible damage and for the presence of ice in the tailcone or elevator assembly prior to flight.


Everyone knows that grease and oil thicken up with the onset of colder weather. Well, almost everyone. Take the case of an Enstrom helicopter operating in -30° conditions, where the pilot was unable to maintain control during takeoff. The subsequent accident investigation revealed that the manufacturer had not taken into account the fact that the grease used to lubricate the flight controls lacked properties necessary for cold weather operations. As a result, the manufacturer was alerted to the problem, and Transport Canada issued an Airworthiness Directive CF-89-17, forbidding the use of Almagard 3751 and Almaplex 1275 lubricants in the Enstrom flight control system.

Engine lubricating oil can be a source of trouble if the oil system is not properly winterized. Winterization includes changing to the correct winter weight oil, then checking that the oil lines or oil tank are lagged (insulated), as specified by the manufacturer’s manual, and that oil cooler doors operate correctly and freely.

The pilot of a Cessna 310 was proceeding en route in -30° temperatures when he noticed the oil pressure rising on the right engine and oil on the cowling. The pilot feathered the right engine and diverted toward the nearest airport. A few minutes later the left engine displayed similar problems. Oil pressure increased, then dropped to zero as the oil supply was forced overboard by excessive, crankcase pressure, and the left engine was feathered. The right engine was restarted and sufficient power was obtained to stabilize the flight. Fortunately, a second aircraft appeared on the scene and managed to direct the troubled pilot to a nearby airstrip, where he landed safely with smoke and oil pouring from the engine. The oil supply for both engines had been depleted due to ice formation blocking the inside of each engine crankcase breather line. Most aircraft maintenance manuals refer to special holes or other alternate crankcase breather methods that should be in place to counter ice accumulation in these lines during winter operations.

Fuel systems

The condition of the carburetor heat system and fuel system are major concerns when preparing aircraft for winter operations. The Cessna 150 is most susceptible to carburetor icing and fuel system ice. The following accidents illustrate some problems in this area.

The pilot of a Cessna 182Q was flying from Resolute Bay, N.W.T., at 11 500 ft and above cloud, when the engine started running rough and stopped despite the application of full carburetor heat. The temperature and humidity were conducive to the formation of carburetor ice. After the forced landing, investigators found that, although the pilot applied carburetor heat properly, the engine could not respond because of a malfunctioning carburetor heat valve. The carburetor heat shroud was found split and separated where nine of the 12 shroud rivets had sheared. As a result, the carburetor heat system was unable to counter the carburetor icing. Maintenance personnel must ensure that the carburetor heat system works according to specifications.

A Cessna 150G was climbing out from St. Francois Xavier, Manitoba airstrip, when the engine stopped. The pilot made a successful force landing and no injuries occurred. Examination of the fuel drain fitting located in the centre fuselage belly area revealed signs of ice covering the fitting port. Since no other cause could be determined, it is assumed that this area iced over or became blocked with ice crystals suspended in the fuel, preventing fuel flow. Numerous warnings and articles have been published about the belly fuel drains on Cessna aircraft. Some models of the Cessna 150 are particularly vulnerable. This unobtrusive little drain cap, or set screw, should be removed at every inspection, and the line drained for a few seconds to remove any accumulated water or debris. This is particularly important in the fall before freezing temperatures are encountered.


There are many cases on record where slush has frozen inside wheel pants, locking the wheels and causing the aircraft to nose over on landing. AMEs should also pay particular attention to oleos and brakes because rubber seals and “O” rings tend to leak and break down in extremely cold temperatures. Retractable gear may require servicing with winter weight grease and the removal of corrosive salts or other contaminants from the mechanism if it is to continue to function safely during winter.

Cabin heaters

Exhaust type cabin heaters must be monitored for exhaust leakage into the cabin (see AD CF-90-03 for mandatory requirements). The exhaust system should be inspected for leaks at the beginning of the winter season. Janitrol type heaters should be checked for correct operation and serviced at the beginning of each winter season. A little preventive maintenance is the best protection against in-flight explosion of gas heaters or carbon monoxide impairment of the crew from exhaust type heaters.

Cold weather operations are a fact of life in Canada, and can be performed safely if everyone, including pilots, AMEs and ramp attendants remain vigilant in detecting and correcting winter operational differences before they cause big trouble during flight.

Last but not least, do not forget to remove the obvious hazard such as ice, snow, or freezing precipitation adhering to the aircraft surfaces and possibly inside the turbine inlet ducts prior to flight.

Maintenance of Small Non-Commercial Aircraft

by Joel Virtanen, Civil Aviation Safety Inspector, Operational Airworthiness, Standards Branch, Civil Aviation, Transport Canada

Section 605.86 of the Canadian Aviation Regulations (CARs) requires that all aircraft be maintained in accordance with a maintenance schedule that is approved by the Minister and that meets the requirements of Standard 625—Aircraft Equipment and Maintenance Standard. However, there are exceptions; CAR 605.86 does not apply to ultralight aeroplanes and hang gliders.

Maintenance schedules

Most small aircraft owners use a maintenance schedule found in Standard 625, Appendix B, that is considered to be approved by the Minister. Anyone using the maintenance schedule in Appendix B needs to make an entry in the aircraft technical record that the aircraft is maintained to that maintenance schedule. Appendix B lists the areas that are to be inspected, but it is not a checklist for the inspection.

Standard 625, Appendix C, is part of the maintenance schedule for every aircraft. It lists the maintenance requirements for specific equipment that are due at intervals specified in the Appendix. Annual review of Appendix C items is required to ensure that the equipment listed is inspected at the proper intervals.

Inspection checklist

In respect of an aircraft, “owner” means the person who has legal custody and control of the aircraft. The aircraft owner must develop a detailed inspection checklist that covers all areas included in Standard 625, Appendix B, as the Appendix in itself is not an inspection checklist. The owner can use the manufacturer’s inspection checklist for the aircraft, where the manufacturer has provided one. Where the manufacturer has not provided an inspection checklist, the owner must develop one.

It is important to review the checklist to ensure that it contains all items included in Standard 625, Appendix B. Manufacturers’ checklists may be deficient for several reasons. For example, the manufacturer’s checklist may be out of date with reference to the current standard. A checklist should also include items covering any modifications carried out on the aircraft. An inspection checklist should be detailed enough to cover all wear items on the aircraft in order to maintain the aircraft in a safe flying condition until the next inspection.

Airworthiness directives

The most important thing to remember about airworthiness directives is that compliance with them is mandatory for all aircraft, except those in the owner-maintenance and amateur-built classifications. It is the owner’s responsibility to determine which airworthiness directives are applicable to the aircraft, and to make them available to the maintenance provider. A list of airworthiness directives that could be applicable to your aircraft or equipment can be found on the Transport Canada Web site. If you are not familiar with airworthiness directives, ask your maintainer for help.

Life-limited parts

Some aircraft have life-limited parts that have to be replaced when they reach their life limit based on elapsed time, calendar time or operating cycles. Most turbine engines and helicopter drive systems have parts that are life-limited. It is the owner’s responsibility to ensure that these parts are replaced at proper intervals. Life limits do not apply to aircraft operated under a special certificate of airworthiness, to owner-maintained aircraft or to amateur-built aircraft.

Inspection intervals

Most small aircraft owners are familiar with the 100-hr inspection or the annual inspection. In 2007, Standard 625.86(2)(a) was modified with respect to the meaning of “interval”. The “annual” inspection is no longer due 12 months from the last inspection, but rather on the last day of the 12th month. This means that if the last “annual” inspection was carried out on January 1, 2011, the next inspection is not due until January 31, 2012. In this case, the effective inspection interval is 13 months less one day. This applies to any interval that is stated in months in the Standard. If the interval is stated as “annual”, it means 365 days. As tolerances are not permitted for aircraft maintained under Standard 625, Appendix B, the inspection interval cannot be exceeded.

Logbook entries

In some cases, all items with respect to the maintenance work done on the aircraft are entered in the aircraft journey log. This is permitted in the case of a balloon or a glider, or an aircraft operated under a special certificate of airworthiness in the owner-maintenance or amateur-built classification. In all other cases, only maintenance items listed in CAR 605, Schedule I, must be recorded in the aircraft journey log.

CAR 571.03 requires that the details of all maintenance and elementary work be recorded in the aircraft technical record. No logbook entry is required for servicing. An entry must be made in the aircraft journey logbook for the date, air time, operating cycle or landing at which the next scheduled maintenance action is required. In this way, the pilot is kept informed of the next maintenance action to be performed.

For more information on recreational aircraft in Canada, visit the Transport Canada recreational aircraft Web site at

2012-2013 Ground Icing Operations Update

In July 2012, the Winter 2012–2013 Holdover Time (HOT) Guidelines were published by Transport Canada. As per previous years, TP 14052, Guidelines for Aircraft Ground Icing Operations, should be used in conjunction with the HOT Guidelines. Both documents are available for download at the following Transport Canada Web site:

If you have any questions or comments regarding the above, please contact Doug Ingold at

Worth Watching—Again! The FAA In-Flight Fire Fighting Video

Developed by the United States Federal Aviation Administration (FAA) with assistance from Transport Canada Civil Aviation (TCCA) and other aviation authorities, this excellent video addresses how to prevent, react and deal with in-flight fires. It’s time well spent!

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