Strip trials
Hi Coffman,
Initially we wanted to do data collection on a runway in order to prove ODM numbers but were told that that wasn't needed as HATS had done work on it plus they had collected data for grass strips. Beaches were easy. 1 or 2 guys at touchdown end with handheld GPS, watch for touchdown then go to the mark and take GPS readings. 1 guy at the stop area with GPS. When stopped he came to ac and GPS marked nosewheel position. Same at start of take-off point and rotate point. Nav backed up with onboard Mark on his kit. Met and surface conditions noted by ground party and by us on flightdeck. Gravel slight change as 2 guys for each event position, spread out at each then forward on a bearing to establish each GPS position. X / head wind component from us and ground party data. Groundspeed at touchdown from us.
Flying it was easy enough. Main point was to be very accurate on speeds and straight at touchdown and to be very consistent. Start of the take-off run had to be gradually moved forward as we dug bigger and bigger dents when powered up to full power against the brakes.
Some of the J work was done using squadron pilots in order to qualify them. This gave some inconsistencies but these were noted by the instructor and gave us a set of data deviations that could be used in the analysis. Use of both Saunton and Pendine gave more data points. Generally beach work is done as the tide starts to ebb in order to give as much time as possible before the tide was due to take the beach back. This would have meant that the sand was always wet so timings were adjusted to give differing degrees of wetness / firmness.
Trials Management Officer (brains the size of planets these guys) and I worked out a spreadsheet to help analyse the data. Hours of pouring over the ODM graphs and establishing baselines from me and geek bits from the TMO). Once complete everything was sent off to guys with brains the size of even bigger planets at Waddington to do all sorts of number crunching. (As a simple airframe driver I would have taken the largest and smallest away then divided the sum of the rest but that doesn't work for statisticians and analysts) They then worked out the factors required for each case.
Some of the J work was also done on later sorties using squadron pilots in order to qualify them. This could lead to some inconsistencies but these were noted by the instructor and gave us another spread of data.
As an aside, using a cone penetrometer could take ages on a natural surface. A fast run with a landrover without going through or sinking worked well. Another non-scientific guide was to use an old fashioned biro pen cap. Push it into the grass holding the tang end. If it didn't go in beyond the start of the tang with reasonable force you were probably good to go. No use on sand.
Another aside. Years ago the powers that be realised that the 146 was only cleared natural surface grass. In case the Queens Flight ever had to use a beach I was tasked to teach the 146 QFI beach landings in a 146. Great chance to do something different but it never went ahead. Powers that be decided it would be difficult to justify a 146 being damaged if there was a problem and we couldn't get off before the tide came in. As we shutdown on beaches for FARP/ALARP I asked why it was ok for us. Told that although 3 engine take-off wasn't allowed from natural surface they were sure that we wouldn't leave the ac on the beach - basically don't ask!