07 December 2009

"DED"-RECKONING AND SLIPPERY RUNWAYS!

THURSDAY 26th NOVEMBER
Not a fantastic day weather-wise with a 2000-2500' cloud base and a briskish westerly of 15-20 knots but a good day to try a bit of "Ded" (i.e.; deduced) reckoning with the Archer III, WIT, partly as a test of my navigation skills and also to deduce a working TAS for WIT for future reference.
I had made a flight plan for a short local cross-country; Hamilton to Port Waikato, down the coast to Raglan and back to Hamilton - 91 miles. Familiar territory and no need to rely on anything other than maps and my calculations. I did use the autopilot to keep a constant heading which would test my drift allowance and so the accuracy of the wind forecast.
With the westerly wind I was given 25R to take off from and started the stopwatch just after rotating off the runway. After levelling off at 2000' (I was given the clearance while still below 1000') I set my calculated heading and engaged the autopilot.
Keeping a constant heading I was able to read map to ground and check the landmarks for halfway, right on the line so wind forecast OK, and arrived over the river mouth at Port Waikato. Turned South down the coast, resetting the stopwatch and heading for Raglan. same procedure at Raglan and home to Hamilton.
The radio traffic was busy and I had to hold at Temple View, so the time was taken there and, two orbits at Rukuhia later I landed nice and smoothly on 25R. (It wasn't perfect, Though - Ash had watched me and reckoned I hadn't flared enough and landed a bit on the nosewheel - ooops.)
Back home with my timings I "back-calculated" my groundspeeds into true airspeed (remembering to allow for ending at Temple View on the last leg) and got the following for the three legs: 126kt, 121kt and 110kt (average 119). Given these I will, in future, use 120kt TAS for WIT and should not go too far wrong. Anyone reading this who reckons I am way off beam please feel free to let me know, thanks.

THURSDAY 3rd DECEMBER
A very showery day but I still went over to the club in the hope of getting up in one of the Robins which I hadn't flown for about two months, a case of keeping current. It was raining when I arrived with poor visibility but cleared sufficiently after a cup of tea for instructor Marie to sign me out to go for some circuits.
Back in the little Robin, I found myself back in very familiar territory and did a pretty fair set of four circuits with two glide approaches, one normal and, finally, a flapless approach - the weather looked like closing in again. Coming in flapless I was, of course, a bit faster than usual and just after landing, I touched the brakes to slow down before the taxiway and that is when it got interesting. The seal was still pretty damp from the earlier rain and I found myself skidding towards the terminal!! Off the brakes, straighten up, still sliding a bit, and let her slow down on her own - after all, there is over 2km of runway on the main 36R - plenty of room to stop. A good lesson on (not) braking on wet runways!!!
Other than the skid, I was pleased with my efforts and current again on the little Robins. Might get to fly in some nice weather sometime!!

No comments:

Post a Comment