After a less than perfect landing at Ruhengeri yesterday afternoon, it became clear that we would not be able to depart Ruhengeri with 4 on board, along with luggage. The relatively high temperature, combined with an altitude of 6,100 feet ensured that the performance of our small turbine was degraded enough to prevent a successfull takeoff from the worst runway I have ever landed on. The problem with this grass runway is that it is fairly uneven and full of holes and ruts. This prevents the aircraft with its relatively small tyres to build up speed fast enough for a successful takeoff.
I made the decision yesterday to depart early the next morning, hoping that the temperature would be somewhat lower than later in the day and without passengers or luggage. My chances for a successul takeoff would be much greater under those conditions, but not guaranteed. What is interesting to note in this context is that there is no specific performance data available for our aircraft, as it is a "conversion", whereby the original piston engine of 310 hp has been replaced with a turbine developing 450 hp. Under "normal" conditions, the performance of this conversion is infinitely better than the original, but to save on certification costs, the manufactuer of he conversion simply states that "performance is equal or better than the original". This may be so, but one gets used to relying on 450 hp performance and expectations for various conditions are along those lines. We had already learned about the loss of performance due to altitude / temperature during our world flight two years ago, but that experience had to be re-inforced once more. To put things into perspective, we can take off under good conditions using less than 400 meters of runway. At Ruhengeri I had more than 1400 meters available.
To be fair, I consulted with the briefing office in Kigali regarding the condition and useability of the runway immediately before departure and was told that all was good. Well, all was not good and the result was as described above.
Without going into technical details, let's just say that I made a successful takeoff with a very narrow margin this morning, using every "trick in the book" to obtain maximum power from the turbine. What makes such takeoff difficult in our aircraft is that visibility becomes nil immediately after takeoff due to a stretched nose section. This is not very helpful when trying to avoid obstacles like trees, buildings and a mountain that were all lined up in my takeoff path. The way to handle this is to have a very clear plan and a memorised image of what the required takeoff path must look like. This morning that meant turning right about 30 degrees shortly after takeoff, to avoid a mountain directly ahead which I would not be able to clear. The height and position judgement during this procedure needs to be performed with visual clues from the side windows only. This is not for the faint of heart and not something I would willingly plan on doing.
It wasn't easy for me to turn down Jürgen's multiple requests to accompany me on this mission (what a brave man!), but I am glad I stayed firm on my original decision to go it alone, as another 90 kg or so could have destroyed the available margin.
Anyhow, all is good now and I am sitting in a cafe at Kigali airport, able to catch up on paperwork. The rest of our group is tracking Gorillas this morning and will hopefull join me during early afternoon and we will attempt to fly to Kamembe. Unlike almost all other airports of our trip, Kamembe, despite being an international airport of enry, does not have any instrument landing procedures. This means that we will be highly weather dependent for our landing there this afternoon. If the weather at Kigali and the forecast for Kamembe is good, we will attempt the flight, knowing that if conditions aren't suitable we will need to turn back to Kigali. The flight time is only around 30 to 40 minutes.
So stay tuned, things remain interesting.
I made the decision yesterday to depart early the next morning, hoping that the temperature would be somewhat lower than later in the day and without passengers or luggage. My chances for a successul takeoff would be much greater under those conditions, but not guaranteed. What is interesting to note in this context is that there is no specific performance data available for our aircraft, as it is a "conversion", whereby the original piston engine of 310 hp has been replaced with a turbine developing 450 hp. Under "normal" conditions, the performance of this conversion is infinitely better than the original, but to save on certification costs, the manufactuer of he conversion simply states that "performance is equal or better than the original". This may be so, but one gets used to relying on 450 hp performance and expectations for various conditions are along those lines. We had already learned about the loss of performance due to altitude / temperature during our world flight two years ago, but that experience had to be re-inforced once more. To put things into perspective, we can take off under good conditions using less than 400 meters of runway. At Ruhengeri I had more than 1400 meters available.
To be fair, I consulted with the briefing office in Kigali regarding the condition and useability of the runway immediately before departure and was told that all was good. Well, all was not good and the result was as described above.
Without going into technical details, let's just say that I made a successful takeoff with a very narrow margin this morning, using every "trick in the book" to obtain maximum power from the turbine. What makes such takeoff difficult in our aircraft is that visibility becomes nil immediately after takeoff due to a stretched nose section. This is not very helpful when trying to avoid obstacles like trees, buildings and a mountain that were all lined up in my takeoff path. The way to handle this is to have a very clear plan and a memorised image of what the required takeoff path must look like. This morning that meant turning right about 30 degrees shortly after takeoff, to avoid a mountain directly ahead which I would not be able to clear. The height and position judgement during this procedure needs to be performed with visual clues from the side windows only. This is not for the faint of heart and not something I would willingly plan on doing.
It wasn't easy for me to turn down Jürgen's multiple requests to accompany me on this mission (what a brave man!), but I am glad I stayed firm on my original decision to go it alone, as another 90 kg or so could have destroyed the available margin.
Anyhow, all is good now and I am sitting in a cafe at Kigali airport, able to catch up on paperwork. The rest of our group is tracking Gorillas this morning and will hopefull join me during early afternoon and we will attempt to fly to Kamembe. Unlike almost all other airports of our trip, Kamembe, despite being an international airport of enry, does not have any instrument landing procedures. This means that we will be highly weather dependent for our landing there this afternoon. If the weather at Kigali and the forecast for Kamembe is good, we will attempt the flight, knowing that if conditions aren't suitable we will need to turn back to Kigali. The flight time is only around 30 to 40 minutes.
So stay tuned, things remain interesting.
