Story by Phil Henderson. Edited by Timothy Webb.
Mark and Diane Vanderkooi live and work with the Kwong people group in the village of Tchaguine in southern Chad. Mark first arrived in Chad 30 years ago as a single young man in his 20s and started out with TEAM, a mission agency, in Tchaguine. After meeting Diane on an MAF flight they married and continued to minister in Tchaguine, helping to design and build a clinic and a radio station.
The Vanderkoois use MAF regularly as the roughly 400 km road to Tchaguine becomes extremely difficult in the rainy season. Mark takes a great deal of responsibility for the airstrip in Tchaguine by keeping it clear of debris, knocking flat the ant hills which sprout up from time to time, filling in any soft areas with clay and helping the local population to position their houses a safe distance from the airstrip.
Leading up to the flight he shared his growing concern that recent rains would make the airstrip too soft to allow the MAF Caravan to safely land and take off again without getting stuck. In our experience if it has not rained in the last 48 hours then the airstrip will be firm enough for a landing and takeoff. Satellite imagery showed a storm had passed over Tchaguine only 24 hours before the scheduled flight and Mark was having difficulty reaching his contact on the ground to determine how much rain they had received. We were ready to push the flight back a day if needed.
On the morning of the scheduled flight, just half an hour before the planned departure, we got word that there had been a storm but the majority of the rain had fallen north of the airstrip. The strip itself had not received much at all. With that information, I made the decision to go ahead and we loaded 750 kg of supplies and passengers onto the plane.
Approaching the village I saw a lot of standing water to the north but thankfully on the low pass over the strip it still looked dry. I came around again and executed a soft field landing in which the nose stays off the ground longer and the main wheels gradually come in contact with the airstrip giving me time to judge how the ground is receiving our weight and ensuring we don’t wheelbarrow straight into deep wet sand.
The strip was definitely soft, but acceptable. Our main wheels were creating 1 to 2 inch depressions and at the end of the strip where I turned around my inside wheel left a sizeable divot as it began to turn on itself and dig into the soft sand. Adding a bit of power and straightening out of the turn ensured that it didn’t dig in any more.
Whenever you are operating in and out of a soft airstrip, the landing is usually going to be easier than the takeoff. A soft surface creates a lot of resistance which is great for slowing down after a landing but not ideal when you need to be accelerating to a speed which will allow the plane to get off the ground. For this reason, MAF has stringent operational margins that must be calculated and applied to all takeoffs but they become especially important in such soft field situations.
It is normal for a pilot to walk the length of the strip before takeoff to gain a good understanding of the surface and the hazards. Then it is necessary to spend some time calculating the acceleration and takeoff distances to be sure that it can be done safely with acceptable margin. We set up an acceleration point early in the takeoff roll to check that we are achieving the necessary acceleration - if not, we have plenty of room to abort the takeoff and go back and recalculate or shed some payload.
When we are going for the takeoff we taxi back to the end of the runway, make a wide turn and go straight into the takeoff without stopping so we don’t risk sinking in and keeping the weight off the nose so we don’t wheelbarrow. A quick confirmation that I have reached my necessary airspeed by the acceleration check point, some negotiating the rudder pedals as the main wheels move through patches of soft and firm ground as we approached the middle of the strip, and then…liftoff. As we lifted off, hundreds of children lining the airstrip clapped and cheered, excited that the takeoff was successful.
