Rob's Safety Briefs
Rob's Safety Briefs
* Safety First
* Do's and Don'ts of Airmanship
Fuel or Water?
The following article on Fuel Tank water drain checks has been reproduced from the Aviation Safety Digest.
The pilot completed the daily inspection and preflight checks on his Cessna 182 and everything appeared normal. However, just as the aircraft became airborne the engine stopped. Fortunately for the pilot he was able to land the aircraft straight ahead on the remaining runway, without further mishap.
Initially, the pilot was adamant that there had been no sign of water in the fuel during his preflight drain check. He also confirmed that there had been fuel in both tanks and that the fuel selector had been turned on.
The pilot subsequently checked thoroughly the fuel remaining in his aircraft's tanks and found that in fact it was heavily contaminated with water. Indeed, the sample he had taken from the tank water drains during his daily inspection had been all water! Because the liquid he had drained seemed the same colour as the fuel the aircraft used and there were no signs of contamination, he had assumed that the liquid was uncontaminated fuel. About 135 litres of liquid were drained before all evidence of water was removed.
There are two important aspects of this incident, namely, how the water got into the fuel and why the pilot failed to identify the problem during the daily inspection. While the question of how the water got in the fuel is most serious, it is the latter issue with which this article is concerned.
The report from the Bureau of Air Safety Investigation confirmed that the original sample taken by the pilot was all water. The report continued: 'Pilots should become thoroughly familiar with the characteristics of aviation fuels and if a sample is of uniform consistency (as in this case), the fact that it is fuel can and must be verified.
One method of doing this is to drain the sample into a vessel that already contains a sample of known fuel. If the sample from the aircraft is all water, it will be readily visible. Another 'ad hoc' method is to pour a little of the sample into the palm of one hand: if it is fuel it should vaporize and leave the skin dry; it will also feel cool as it evaporates. Water will remain on the skin. The sense of smell should also be used to help with identification.
The size of the fuel sample taken is important, as it must be sufficient to be conclusive. It will vary depending on the fuel capacity of the particular aircraft.
Check on the amount you need to take from each drain on your aircraft, either in the aircraft operating manual or from an appropriately qualified engineer, to ensure a positive result.
Finally, the point need to be made that the fuel/water checks discussed above should be used only when more positive tests cannot be made. If a visual check is inconclusive, then the best and only certain way to ensure your fuel is free from the danger of water contamination is to test a sample with water sensitive paste or capsules.
Rob's Note: For the aircraft we operate at Curtis Aviation, a full single fuel drain per tank is acceptable. I always do a full drain on the first tank, and once positively confirmed that what I have drained is actually fuel, and not part water or all water, I then discard half, and then drain from the second tank.
Seats that unlock...
In recent times there has been an accident and a number if incidents relating to seats becoming unlocked either during ground maneuvering or during the take-off. In the recent Victorian accident the pilot lost control of his aircraft immediately after take-off resulting in a fatal accident.
Many of our pilots have learned to fly in the Citabria which only has a seat that can be moved into two different positions, however, aeroplanes such as the Warrior, Dakota and the Cessnas have seats that will move a considerable distance rearward should they unlock at a critical stage of flight. This will then result in the pilot usually hanging on to the control column as the seat moves rearward resulting in a steep pitch up of the aircraft. The pilot may also attempt to hang on to the throttle, closing the throttle, which with the high nose attitude will result in a stall, and the consequences of this happening close to the ground do not bear mentioning.
The pilots operating handbooks for some popular aircraft types include the pilot's check of the adjustment and locking of seats, belts and shoulder harnesses in the 'before starting engine' checklist but not in the take-off checklist. Others do not include a check of the seat itself, mentioning only seat belts and harnesses. As some pilots find it necessary to adjust their seats, 'belts, harnesses and seat locked' should be included in the 'before takeoff' and 'before landing' check. The security of the seat should be should be tested with firm back pressure after checking that the adjusting mechanism is in the lock position.
The seat is often stopped in the desired position by a locking device linked to a bar or handle for use by the pilot in releasing or locking the seat in place. Most seats are locked by pins which slip down into holes in the track, although a few use other devices such as clamps or 'shoes'. A security stop at the end of the rails prevents the rollers from overrunning the tracks.
The adjustment mechanism is usually spring loaded, so that when the handle is released the pins drop automatically into the locking slot. However, in some cases there is no spring and the pins must be manually positioned or the seat will slide under pressure.
A training aircraft, flown by pilots of varying size, will have its front seats shunted back and forth frequently, subjecting the movable mechanism to considerable wear and occasional abuse by the impatient pilot. This may lead to the end stops becoming weak and prone to overriding, or to the intermediate stops becoming enlarged and prone to slippage. For these reasons, a periodic check of the mechanism is included in the maintenance requirements. The following is a list of the checks carried out by LAME during periodic maintenance and it is considered vital that pilots carry out these checks during the daily inspection as wear and tear may have taken place since the last periodic inspection. This inspection should include the following:
· The metal framework of the seat, particularly the joints.
· The rollers and roller brackets - check for proper alignment and wear.
· The locking mechanism, including the actuating arm, linkage and locking pins - make sure the release spring, if there is one, is intact, and the action is positive.
· The floor mounted rails - make certain they are tight to the floor and tracking true; the rail stops should be clear and not distorted, and the end stops solid.
While you have your nose down on the floor, this is a good time to remove any foreign or loose objects hidden under the seat. Coins, combs, keys and other abandoned miscellany take malicious delight in jamming vital mechanisms at the worst possible time.
Do's and Don'ts of Airmanship
¨ Do shut down your engine before loading or unloading passengers.
¨ Do warn people to keep away from the propeller and not to touch it for any reason.
¨ Do taxi at a speed from which you can come to a stop at any time.
¨ Do have someone on each wing tip for guidance when taxiing in confined spaces.
¨ Do taxi at night only on lighted taxiways.
¨ Do leave the controls locked after parking the aircraft.
¨ Do set the brakes or chock the aircraft on the apron.
¨ Do tie down the aircraft when parking overnight.
¨ Do use the radio only for what it was intended - and keep the channels open for operational or emergency messages.
¨ Don't start your engine before being assured your propeller is clear.
¨ Don't start your engine with the aircraft's tail towards other aircraft or open hangars.
¨ Don't start your engine while people are standing in front or behind your aircraft.
¨ Don't use high power while taxiing in close proximity to other aircraft.
¨ Don't conduct a long pre-flight run-up in the vicinity of offices or occupied buildings.
¨ Don't ask for weather information right after take-off - you can check it by Internet, fax or telephone before departure.
¨ Don't taxi on to an apron at a fast rate. Your brakes could fail.
Carburettor Icing
This is the time of the year when carburettor icing is likely to catch some pilots unawares - that is, unless they are ready to take positive, correct action to counter the condition as soon as the very first symptoms of carburettor icing appear.
Uncertain, hesitant, “fiddling" with carburettor heat control can often do more harm than good (by raising the carburettor air temperature just enough to put it in the optimum icing range) and the stage can quickly be reached where the engine has lost too much power to be able to provide the heat necessary to clear the accumulated ice from the throat of the carburettor. Take this case for example:
On the northern tablelands of New South Wales, a pilot was making a private cross-country flight in a Cessna 150. Some 15 minutes after take-off, while cruising normally at about 4,000 feet, the engine began to run roughly. Believing the trouble was carburettor icing, the pilot operated the carburettor heat control several times but the rough running continued intermittently. The pilot then decided, that as carburettor heat did not seem to be rectifying the trouble, to return to his departure aerodrome. Soon after turning back the rough running worsened and even with full throttle applied, the engine continued to lose power.
Eventually the pilot realised he would have to make a forced landing. He selected a suitable paddock, transmitted a MAYDAY call and commenced an approach. By this time the engine was running extremely roughly and the maximum r,p,m. had dropped to 1,600. Turning on to final approach, the pilot closed the throttle and the engine stopped completely. The forced landing was nevertheless successful and the aircraft was not damaged.
Subsequent examination of the engine failed to find any fault and after a satisfactory ground check, the aircraft was flown back to its base without further trouble. It was established that the existing meteorological conditions were favourable to the formation of carburettor ice and it was learned that another pilot who was flying in the same area at the time had experienced a tendency for carburettor ice to form. In the circumstances, there was little doubt that carburettor ice was the cause of the engine trouble and that the pilot has not used the carburettor heat control correctly to counter its development.
The Australian Safety Digest published an article recommending the use of full carburettor heat at frequent intervals in suspected icing conditions to check for the presence of ice. The article also pointed out that carburettor heat must be applied for long enough - 30 seconds was suggested - to rid the induction sytem of the ice that had formed. It seems clear, however, that the pilot of the Cessna 150 did not appreciate this point. When his application of carburettor heat did not immediately cure the symptoms he was experiencing (and probably further caused a further, though very temporary, loss in power), he concluded that carburettor heat could not correct the trouble.
The pilot's reference to gradually increasing the throttle opening, eventually to full throttle, to try and compensate for the loss of power is also significant. The digest article pointed out that this set of circumstances can lead to a complete loss of power if sufficient carburettor heat is not applied long enough to overcome the rapidly increasing accumulation of ice in the induction system.
There may be some pilots who, on reading of this incident, feel that they too may be a little “rusty" on the theory of carburettor icing. There may be others who have not yet experienced symptoms of carburettor icing themselves and who may not be fully confident about using the carburettor heat control in flight. Pilots who believe they may be in these categories should obtain a thorough briefing on the subject from any of the Curtis instructors (experienced in the type of aircraft they intend to fly), before venturing off into conditions in which carburettor icing is possible.
It is important to remember too that these conditions are not confined only to cold weather. Carburettor icing can occur on quite warm days if the humidity is high enough. For example, with a relative humidity of 60%, and outside air temperature between 5OC (41O F) and 27OC (81O F) can be conducive to the formation of carburettor ice.
Autumn Weather
Autumn generally sees the progressive transition between the weather experienced in summer to that in winter, with features of the summer scene often persisting into early autumn and features of the winter scene often evident in late autumn.
Generally good flying conditions are experienced during the daytime in mid-autumn. However, pilots should be wary of:
·Carburettor icing, particularly if flying in low level moist onshore streams.
· Running out of daylight as the days are rapidly shortening
· Increased incidence of fog/low cloud.
Average number of fog days (per month) at various locations showing increased incidence from late summer through autumn, for example are:
FEB MAR APR MAY
YSCN 2 5 7 9
YSCB 1 3 4 8
Late autumn generally sees an increase in the frequency of cold frontal and stream weather along the southern coastal areas of Australia. With these fronts are wind changes, often low cloud, reduced visibility, precipitation, wind shear and turbulence.
While talking in very broad terms about ‘average' autumn weather, large variations from the ‘average' may be experienced, e.g., a late season tropical cyclone affecting northern coastal areas, an inland deep low pressure system or an upper air disturbance leading to very poor flying conditions. The principles of ‘weatherwise' flying must always be observed even at this generally ‘weather benign' time of the year. Anticipation and proper preparation are the key elements to obviate any potential problems that may arise.
