Date of Accident: 5 April 2002
Time of Accident: 0500
Aircraft Registration: ZS-EBM
Type of Aircraft: Piper PA-28-140
Pilot-in-command
Licence type: Private
Licence Valid: Yes
Age: 18
Total Flying Hours: 80.8 hrs
Hours on Type: 77.1 hrs
Last point of departure: Escourt (100 nm NW of Durban)
Next point of intended landing: Escourt
Location of the accident site: Giant’s Castle Reserve at an elevation of 6000 ft.
Meteorological Information: CAVOK
Number of people on board: 1+1
No. of people injured: 1+1
No. of people killed: 0
Synopsis
The private pilot was accompanied by a passenger on an aerial stock-theft patrol flight in the Drakensberg Giant’s Castle area when the accident occurred. The aircraft departed Escourt aerodrome at 0420Z with approximately 40 US Gal. of fuel on board.
Approximately 40 minutes later, the aircraft was approaching a mountain range in the Giant’s Castle area while flying in a Westerly direction. The aircraft had flown up the valley at an altitude of approximately 6800 ft and was in the process of turning away from the mountain to turn around and head back down the valley again when he apparently experienced a strong down draught, which caused the aircraft to descend.
Due to the rising terrain in the direction of flight, the aircraft collided with terrain on the Eastern side of the mountain while in a shallow banked turn to the left.
The aircraft came to rest approximately 35 m further on and was substantially damaged.
The pilot and passenger sustained minor injuries in the accident.
Probable Cause
It is believed that the pilot was flying towards the lee of a mountain range at a relatively low altitude with only a small margin in terms of terrain clearance height, which necessitated the pilot to turn away from the mountain in order to avoid a collision. Due to the aircraft flying into the lee of the mountain, the pilot encountered a downdraught, which caused the aircraft to descend into the rising terrain.
Jim's Analysis
Okay, let’s start with my old faithful question: when would you not be happy to be in the back of this aeroplane? I am afraid that if the pilot reads this he is going to be very offended by my answer.
The truth is that I would never have got in the back of the aeroplane. Why? Well let’s have a look at the things that were likely to contribute to the sad outcome.
- The pilot had very few hours. In all probability he had just completed his PPL.
- He was only 18 years old. Now I am not saying all 18 year-olds are unsafe pilots – many may be extremely cautious and safe. But the odds are not in favour of youngsters. Insurance companies, for both pilots and drivers, have learned, from long experience, that this is the age bracket that poses the highest risk.
- The aeroplane was not ideal for mountain flying – simply because of its lack of power. At that sort of density altitude the aircraft would have had a rate of climb, at gross weight, of about 380 ft/minute, compared to nearly double that at sea-level.
- The tanks were 80% full. So the little aeroplane was probably getting close to gross weight.
- Stock-theft patrols are conducted close to the surface.
- He was operating at nearly 7000 ft in an area where the mountains tower to just short of 11,000 ft.
- Although the meteorological information is reported as CAVOK, it fails to mention the wind. However the pilot claims that it was the wind that caused the accident.
- The report says “Due to the rising terrain in the direction of flight…” – this is very bad news.
Folks, the last two points tell me that the pilot had not had any mountain/canyon-flying training. If he had, he would have known that two of the golden rules are that you do not fly amongst mountains in the wind, and you do not fly up slopes – you fly down them.
What Can We Learn
I am going to use this as an excuse to give you a very brief summary of the main lessons to be learned before you fly in mountainous areas.
- Don’t try to teach yourself mountain flying – this guy did and he was very lucky only to write-off the aeroplane, and not to kill himself and his passenger. You must go on a recognised course before you fly anywhere near mountains.
- One of the first things the course will teach you is to find a comfortable “canyon speed” to fly at. This is the speed that will give you plenty of manoeuvrability without being too fast. You will probably find that you want to be somewhere around your best climb speed with 10° or 20° of flap. If you go too fast you may encounter obstacles quicker than you can handle them. Also high speed means a large radius of turn. Once you have found the “canyon-speed” for that weight and density altitude, then notice the power settings you need to maintain it in straight and level flight. When canyon flying, you want to have your eyes outside as much as possible, so selecting a power-setting means you don’t have to keep looking at the ASI.
- Now we run into a new problem. In a canyon the horizon, your main source of attitude-reference, disappears. This means that it is very easy to run out of airspeed by subconsciously easing back on the stick as you approach rising ground. My guess is that this pilot did exactly that.
- It also means that your bank reference disappears – so you have to be ultra cautious about not banking too steeply.
- I am sure you can see a conflict of interests here. You should keep your eyes outside, but you need to regularly check on your airspeed and bank. So you just have to learn to do both. Mostly outside, but with quick, regular glances at the instruments.
- If you need to turn round, obviously you want plenty of lateral room and a small turning radius.
- To get the most lateral space, never fly in the centre of a canyon – stick close to one wall, preferably the right hand one. There are three reasons for saying this. First, most of us find left turns are more comfortable – we are used to them around the circuit, and they give us the best visibility into the turn. Second, you should be to the right if you meet opposing traffic. And finally, you are meant to fly to the right of line-features – in this case probably the river in the bottom of the valley. But then we have a rule that overrides this – if there is a wind then you fly next to the wall with the updraught.
- Talking of rivers, generally the bigger the river, the wider and less curvy the valley.
- Obviously it only makes sense to fly down the valley. Imagine coming round a corner and finding a massive waterfall in front of you!
- For any angle of bank, the turn radius is proportional to the square of the airspeed. So if you are in a 30° bank at 130 kts you will have a turn radius of 2600 ft, about 800 meters. So the diameter of your turn will be 1.6 kilometres. Now if you reduce speed to 70 knots the same turn will only take 460 meters. A massive difference.
- You are probably asking why we don’t use more bank if we want to turn in a shorter distance. Good question. Certainly with a steeper bank the turn takes less room. The problem is that without a horizon, you can easily become disoriented and find yourself in a far steeper bank than you thought.
- If you are planning on mountain/canyon flying, always have the aeroplane as light as possible. I don’t have space here to go through all the sums, but trust me on this. A Cessna 182 at gross weight gives you X amount of performance at sea-level. If you want to equal this performance at a density altitude of say 8,000 ft, you will need to chuck out two of your 80 kg mates, plus their two enormous 35 kg bags, plus 180 litres of fuel. In other words you will need to be 363 kg (800 lbs) lighter!
- Remember the old warning about valleys. They have been the demise of many pilots who didn’t see the wires
- Finally, if you are not in a valley, but need to cross a mountain ridge, always do it at an angle of about 45°, so you can easily turn away and fly down the slope if you get in a down-draught.
So now would have got in the back of that little 140 Cherokee to go low-flying in the mountains, in the wind, with a young PPL who has just got his licence, and had no training on mountain-flying?