Monthly Archives: juli 2016

STOL Operations General 2

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The minimum speed required to be able to control a multi engine aircraft is the most critical engine fails is called Minimum control speed which has the ICAO standard abbreviation: VMC, meaning Velocity Minimum Control. The normal standard requirement in any commercial flight operations is that a runway is long enough so that the airplane can abort the takeoff run and stop on the runway before reaching VMC. In addition the aircraft should be able to climb above any obstacles during climb out. There are of course some margins regarding take of length and obstacle clearance in addition considering weather and runway condition and some leeway with regard to pilot handling. This is all described in the ICAO STOL manual. More details later.

Some of the Nepal airports could not meet these requirements due to terrain and hence didn´t meet the ICAO requirements. The runways were so short due to the surrounding terrain that take-offs had to be done without the ICAO standard. There were basically 2 ways: 1. Lift-off below VMC and hence having the risk of an engine failure below VMC when airborne which could lead to loss of control, i.e. that the airplane would flip around, or; 2. Lift-off at or above VMC and hence not having enough runway to stop if an engine failed late in the Take-Off run.

We did find ways to mitigate the above risks to an acceptable level, more to come!

STOL Operations General 1

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«A mile of road get you nowhere, a mile of runway can get you anywhere” is an old aviation proverb. It is only partly true since less than half a mile is enough to operate a STOL airplane.

STOL means Short Take Off and Landing. A STOL Port is hence an airport designed for airplanes with STOL capability, i.e. that it can take-off and land shorter than normal aircrafts. The STOL ports are most often built where a regular airport cannot be built due to terrain limitations, or other operational limitations like close vicinity to populated areas. STOL ports can also be built specifically in a network of STOL operations to provide remote areas or smaller communities with the advantage of having an airport. Norway built 30 STOL ports in the Western and Northern regions in the sixties. with daily scheduled routes with Twin Otter aircrafts operated by the Airline Widerøe. The Norwegian STOL port standard was 800 meters long runways, which were suitable for the De Havilland Twin Otter airplanes in uses then. It was long enough to meet the requirement of Take-Offs with a speed which allowed full control if an engine failure on the most critical engine occurred. Below that speed an engine failure would lead to loss of control as the aileron and rudder did not have enough airflow to counter for the yaw / roll caused by asymmetric trust from the live engine and drag caused by the propeller on the “dead” engine.

The STOL mission 4

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The STOL ports was rated in 3 categories A, B and C, as we did in Norway. A was regular STOL ports without any specific challenges. B was more demanding with some challenges when taking off or landing or other restriction with regard to runway  length, conditions or altitude, approach or climb-out. Both A and B STOL-ports could be flown both ways i.e. landings and take-offs could be performed both ways, depending on wind conditions. A C-port was the most demanding a could have multiple challenges with regard to runway length, profile, elevation and obstacles. Most of them would be so called «one way in, the other way out», i.e. approach and landing could only be from one direction and the take-offs would be done in the other direction. The most famous airport was Tenzing Hillary Airport also known as Lukla which is rated as the most dangerous airport in the World. It was the gateway to Everest Base Camp with a lot of activities. Personally I would not call any airport «dangerous», but rather «extremely challenging». Lukla was indeed extreme and challenging as proven by quite a few fatal accidents and near misses throughout the years. Add to that extreme commercial pressure. See a 3 minutes teaser or our 1:05 hr video on Vimeo:

Link: https://vimeo.com/ondemand/thenepalstolmission.

The Nepal STOL Mission 3

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Flying in the Himalayas, with the terrain above me! That was a challenge I could not resist. I applied immediately for the job, got an interview and soon after acceptance. My employer Widerøe Airline, was positive and a leave without loss of seniority was accepted. My wife Wenche accepted also even if she was pregnant with our third child. A boy was born and away I went with Wenches blessings. Just 2 months later she and the 3 children was with me in a nice home in Katmandu. I was checked out on the STOL ports and ready to take over from my predecessor Captain Don Lelievre, a French Canadian.

The Nepal STOL Mission 2

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This adventure started for me in 1985. I was a Twin Otter  Captain in Widerøe Airline in Norway. Widerøe was a domestic airline which connected the Norwegian STOL ports with National domestic and international airports. We where told that they at the time was the Worlds largest Twin Otter operator. The STOL ports covered the west coast mid and northern Norway. The flying was demanding with VFR/IFR operations in fjords an mountainous terrain.The weather was often extreme. The Twin Otters was scarcely equipped, there was no autopilots, weather radars or ground proximity warning systems. The ground equipment on the STOL ports were equally basic with non precision approaches and basic lightning. All this prepared us well for the Nepal STOL mission. When ICAO contacted Widerøe and asked if any pilots would be interested in flying the UN plane in Nepal, they clearly stated that this was due to De Havilland’s recommendation.

The Nepal STOL mission 1

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As I have written about the What, Why, How and When´s and my views on Airmanship, I will now turn over to the practical and maybe ultimate sample of what this is all about. I will write about our STOL mission in Nepal in the mid-eighties where we flew on some of the most critical airports in the World. I use the word critical instead of dangerous as I truly believe that all these airports can be operated on within acceptable safety criteria. I do not subscribe to such terms as «The Most Dangerous Airport» in the World, etc. this is often credited Lukla, also known as Tenzing Hillary Airport. There is no doubt that Lukla and other airports in Nepal are some of the most critical airports in the World. After all it is unusual that most of the flying is done with the terrain above you instead of below you. In such a critical environment we rated the airports in 3 categories: A – B- C. A was the “easiest” ones, while C the most critical. Note that all the mountain airports where STOL ports, i.e. Short Take Off and Landing fields, which demanded precision flying. The proverb: “Any runway gets to short if you land in the wrong end!” has a special and significant meaning there.

Website on hold – starting again!

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I apologize for not having blogged for a while. Thank you to the many positive comments. The NEPAL STOL Mission video is soon available in DVD format. I will focus on text to that extent as it will explain what airmanship is in real life. I will write info on each airport in the video including the various challenges we had when operating them. The operations where on the edge of what can be done in flight, but with the right knowledge, attitude, skills it can be done with acceptable safety margins. So fasten your seat belts and I´ll tell where, when, why and how