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This paper presents an overview of the aviation mishaps that happen due to adverse weather conditions it talks about the general reasons behind the mishaps caused by weather and there is a discussion with reference to two case studies. The first one took place when CESSNA U206F (FLOATPLANE) C-FASO got caught in bad weather and dense fog ending in a collision with terrain. Second is Cessna 172RG flight got caught in cold weather conditions and whiteout and collision with the surface of a frozen lake.
Since the time aviation industry started taking the commercial shape, safety has been the most important and talked about topic. There has been a revolution in the safety features introduced in the past four decades and we can proudly say that we have covered most of the major vulnerabilities that can lead to fatal accidents, but the worry is that the situation is more critical as not only man made factors (the design, pilot’s expertise, signals and radars, other technical factors) there are lot of other natural constraints against which the maximum we can do is to take the best possible measures so as to avoid any mishap but they being natural elements keep the human control away from them and therefore we see accidents happening despite all the steps that we take [AWS01]. ‘Weather’ is that uncontrolled factor and lets discuss what are the common causes of worry and look at two case studies with special concentration on the weather conditions that were responsible for the accident.
As discussed above, weather can play an important role or the primary role behind causing an accident, and if there is any such mishap there are forensic weather experts who try and determine the cause of an accident and do a research to come with a report[AHEA]. There are also several agencies (govt. and non-govt.) that help to keep the weather reports in order to once again assess the condition at the time of accident at a particular place, for ex. In US this is done by the National Climatic Centre which is in Asheville (North Carolina). Let’s look at a few important factors[AWH03]:
- Causes during take off :
- There can be taxi accidents due to the reduced visibility.
- Gusty weather might be the cause of an accident
- This can also happen in wind shear
- Microburst conditions can also cause this
- Causes during cruise :
- Penetrating low visibility area
- Thunderstorm penetration
- Icing Encounters
- Clear air turbulence]
- Mountain wave turbulence
- Encounters with snow, rain or hail etc.
- Causes during landing :
- Runway issues due to reduced visibility
- Turbulence and gusty conditions
- May be due to wind shear
- Can be due to icy or wet runways
- Microburst conditions
There are enough information sources available to guide the pilot about these weather conditions and all the pilots are supplied with a weather report through in house or contract meteorologists. There are preflight briefings related to weather based on the route that he will be taking and it includes the current details and forecasted data during that specific period of time. It is important to keep in mind the weather conditions briefed, warnings that were given, weather at the time of accident and the proposed solution [AWS01]. Further we will see two case studies where weather has played an important role in causing an accident and what were the measures taken :-
Case Study #1 - CESSNA U206F (FLOATPLANE) C-FASO FLIGHT IN WEATHER CONDITIONS UNFAVOURABLE FOR VISUAL FLIGHT AND COLLISION WITH TERRAIN
Plane Type - CESSNA U206F (FLOATPLANE)
Date – 19th October 2006
Owner - Aviation Maurice
Area – Quebec
Passengers – Five
Cabin Members – Pilot (Only)
Casualties - None
The Cessna U206F is an air-craft equipped with one engine and is capable enough to carry 6 passengers, the above mentioned flight involved proper testing and there was no technical reason or shortcoming that can be accounted for the accident.
As far as the flight is concerned it was basically for sightseeing and hence the time of travel was supposed to be approximately 20 minutes and the departure was a little delayed considering that the weather was not suitable for flight. There was an estimate announced for the ceiling and the visibility which was 1100 Feet and 6 Miles respectively, this was in accordance to the Canadian Aviation Regulation and hence the flight was approved to take off with a scheduled departure to be at 1020, from the day visibility point of view it was expected to be 1 Mile while flying below 1000 feet (Visual Flight Rules) [PCI] .
The departure took place per the scheduled time however as soon as the flight took off the condition of the weather deteriorated, but they continued flying and after some time when the flight was about eight miles from the departure point and there was a message sent by the pilot to his chief who was following in another plane about the dense fog that he had entered into, he also clarified that considering the unpredicted environment he will take a 180o turn. While further proceeding the plane entered very thick layer of fog thus making the pilot loose the visual reference with respect to the ground and he suddenly realized trees approaching from below and tried his best to apply the maximum power to gain the required height and clear the path, however it was too late and the left float had by then clipped to a tree making the plane go downward and then fall on its back.
Now the analysis goes like this, the flight took off early in the morning and at that point of time it had taken off it was already expected that the weather might not be good, but considering 6 miles visibility it was decided that the flight could be operated as ideally the danger approaches only when the visibility goes below 1 mile, which was not the case here. Since there were majorly mountains the ceiling got reduced to 300 feet and now the altitude and visibility both were low making the accident more probable as it does not allow the pilot a lot of time to react as the obstacles can be seen only once they are too close[PCI] .
Case Study #1 - Cessna 172RG FLIGHT IN COLD WEATHER CONDITIONS UNFAVOURABLE FOR VISUAL FLIGHT (ICING) AND COLLISION
Plane Type - Cessna 172RG
Date – 15th October 2000
Owner - YUKON TERRITORY
Area – Quebec
Passengers – One
Cabin Members – Pilot (Only)
Casualties - Two
This incident had taken place when a pilot along with one passenger were travelling from Whitehorse to Dawson, the distance is somewhere around 240 Nautical miles, it was cold weather and the pilot had taken a general weather briefing for the route that he was supposed to take. The pilot started the flight and proceeded towards Lake Labarage, now this was a little colder area and the weather also did not prove to be favorable enough and therefore there was a message sent by the pilot to his earlier base that he will be descending to somewhere around 300 miles, this step was taken in order to enhance the visibility which was effected due to the snow fall[PCI] .
Within half an hour’s time the ground clearance was dropped to 200 miles and the pilot kept on flying with that altitude for a while and moved towards north of the fox lake. All this happened within a period of two hours and the wreckage was discovered shortly after this with both the pilot and passenger found to be deceased. The debris was found at the frozen fox lake with the nose of the plane hitting the surface at 20 degrees and the plane was damaged beyond repair. Now let’s do a short analysis to determine the possible reasons for this mishap; primarily the conditions were not that worse when the flight was approved visibility of 6 miles is definitely good enough for everything to happen smoothly. Then what could have happened on the day of accident? Let’s first have a quick look at the weather (Whitehorse station), the winds were declared to be 340 Degree Magnetic at 10 Knots with visibility 6 Miles and there was another update which said the winds to be from 320 degrees magnetic 10 to 20 knots however the situation changed drastically at the time when the flight was going on and at that time the wind is expected to be 010 Degrees to 360 Degrees with a velocity of 7-12 knots and similarly the visibility was also announced to drop from 6 miles to 1.5 miles only in snow showers.
Now there can be two situations which might have caused this, Icing or Whiteout, lets first find out more about these two phenomenons and then conclude which one could have been the possible reason behind this. Icing is a very common factor which needs regular check in the area where flying takes place under cold environmental conditions[PCI] ; there are multiple factors which can result into an accident due to icing so whether it affects the wings or screens or effects the weight balance of the aircraft, it can be severe and needs immediate response specially with the light weight planes which do not have an anti-icing system.
Again, Whiteout is a type of Icing which basically is a result of precipitation and hence causing complete loss of visibility dropping to below 0.25 Miles. This is an optical phenomenon in which the observer can only see a uniform white glow. Its does not allow the person to distinguish between shadows, horizon & clouds etc. There are instruments to work this situation out however the small aircrafts are not fitted with these devices.
Now, there is one more factor that was involved is where the pilot took the decision to follow the highway, which was not in line to any guidelines that were laid out but the major role was played by the visibility factor causing a sudden cut off and mismatch of the directions. Now the most probable reason seems to be a whiteout and in that case there would be no possibility of determining through visual reference his altitude above the ground, moreover due to the absence of any visual reference the pilot would not have been even able to turn in order to escape the deteriorating weather.
Now if we summarize the discussion above that though the weather was basically the reason of the accident, the pilot too contributed by not being able to identify the adverse situation in time and responding to it effectively. The pilot flew the aircraft in a whiteout situation and not being able to see the aircraft’s altitude and orientation landed up hitting the surface which caused the damage[PCI] . Most importantly the weather forecast that was received by the pilot had predictions which proved to be wrong, the entire area was suppose to have visibility above six statue miles however only after crossing approximately 25 miles, the visibility dropped to below 1.5 statue miles in snow showers.
Flight experience is an important aspect of training because it allows pilots to learn how they interact with adverse weather. Pilots should be able to interpret visible signs of adverse weather properly, and they should have the flying skills to avoid or escape from hazardous weather that they encounter. – National Aviation Weather Services
Now that we have gone through the above two case studies it is very clear that despite the several other important factors that need to be checked it is also important that weather is given equal importance and specially in the case of small and light-weight aircrafts that are not equipped with required radars and anti-icing equipments[AWH03].
Weather Briefing – It is a mandate for the pilots to take a briefing on weather before any flight and the analysis of weather must include the change in weather with respect to time and path taken during the flight. No matter how accurate is the report the pilot must be always ready as it can get deteriorated anytime hence it is important that beside the flying hours or experience the pilot must be aware of how to handle certain rare happenings and this can be learned by going through case studies[AWH03].
Decision Making – In both the cases discussed above the decision taken by the pilot either proved wrong or it was too late to make any positive impact and hence the accident which could have been prevented took place. Therefore it is very important for the Pilots to take the right decision at the right time as a delay might take things out of ones hand and there might be no other option left.
Now, if we analyze the above graph we will realize that not much of an area is covered by weather related accidents, but if we further move and do a critical study we will find out that weather is directly proportional to most of these and adverse weather can easily cause one of these to give it a shape of a mishap. The last factor which needs very strict consideration is visibility and we can see in both the cases above that even though completely separate phenomenon related to weather were involved in the cause of the above accidents, the result of adverse weather cause loss of visibility completely (as inferred) and therefore the visual ground reference was lost thus causing the accident[DDM03].
Now that we have covered almost all the basic features of weather related accidents, have gone through two case studies and have discussed the precautions it is time to conclude that though weather accidents are very dangerous and highly unpredictable, they are avoidable with a little patience and knowledge. Presence of mind also plays a very important role in order to avoid any such incidents from happening and therefore the aviation industry must take strict steps to ensure that before flying there is enough update on weather and immediate assistance is available in case of trouble[AHEA].
[AARL] Barnes Warnock McCormick, M. P. Papadakis, Joseph J. Asselta : Aircraft accident reconstruction and litigation
[AWS01] National Research Council (U.S.). Committee on National Aviation Weather Services: Aviation weather services: a call for federal leadership and action
[AHEA] Douglas A. Wiegmann, Scott A. Shappell: A human error approach to aviation accident analysis: the human...
[AWH03] Terry T. Lankford :Aviation Weather Handbook