Archive for October, 2007

Wind calculations made easy

Thursday, October 18th, 2007

Hours flown today: 1h10m

Hours flown so far: 27h 55m

Today was the second navigation exercise: Oxford to a remote departure point (I chose Charlbury again, because it’s easy to find from runway 19 by simply following the railway), then overhead Gloucester Airport, Banbury, and back to Oxford. The planning was made vastly easier by the total absence of wind - no calculations required! Just drew the lines on the chart, measured lengths and headings, checked carefully, and off we went.

I forgot to ask Tower for a radio check when I first called up - must remember that. The instructor commented that when taxying out, I should comment on the checks I’m making so the examiner knows I’m doing them. That’s fair comment, because I’d forgotten to do the checks! I felt that the aircraft lurched off the ground rather clumsily, which was surprising in the zero wind conditions, but the instructor pointed out that it was because I’d grabbed back on the yoke to rotate: it should be a smooth action over two or three seconds. So we got off the ground, and I must remember the “ATPL” check:

Altitude 800ft AGL

Transponder to Alt mode

Fuel Pump off

Landing light off

Found the railway, and followed it towards Charlbury. I should have trimmed for the climb immediately after takeoff, rather than trying to hold 75 knots by hand all the way to 2500 ft. Still, the target altitude came up fairly soon, and I established a steady cruise. Time to switch to Approach:

me: “Golf Golf Oscar Airborne, to Approach”

Tower: “Golf Golf Oscar roger”

instructor: double-clicks the push-to-talk. The acknowledgement is not strictly necessary, and a polite “thank you” might be used in the real world, but is slightly frowned-upon by examiners.

<change to Oxford Approach on 125.325>

me: “Oxford Approach, Golf Bravo Tango Golf Oscar, listening out to the West, request Flight Information Service”

Approach: “Golf Bravo Tango Golf Oscar, Flight Information Service”

me: “Flight Information Service, Golf Bravo Tango Golf Oscar”

So we arrived overhead Charlbury - at which point, I turned onto heading for the first proper leg to Gloucester, noted the time and calculated our Gloucester ETA, noted I had nothing to say on the radio, and conducted a FREDA check before settling into map reading. We made a slight detour to avoid overflying the gliding site at Little Rissington, at which point it was time to switch to Gloucester Approach:

me: “Golf Golf Oscar, freecalling Gloucester Approach”

Oxford Approach: “Golf Golf Oscar roger”

me: double click the PTT

<switch to Gloucester Approach on 128.55>

Now the fun begins! The instructor pulled out his pre-prepared script card for this lesson and held it for me:

me: “Gloucester Approach, Golf Bravo Tango Golf Oscar, request Flight Information Service”

Gloucester Approach: “Golf Bravo Tango Golf Oscar, Flight Information Service, pass your message.”

Now, the crucial acronym here is TRPACER:

me: “Golf Bravo Tango Golf Oscar is a (type) PA28 from (route) Oxford to Oxford via your overhead and Banbury, (position) currently ten miles east of Gloucester at (altitude) 2500ft on QNH 1025, (conditions) VFR, ETA your overhead at 18, (request or acknowledgement of request) Flight Information Service, Golf Bravo Tango Golf Oscar”

Gloucester Approach: “Golf Golf Oscar, Cotswold QNH is 1022, report overhead Gloucester”

me: “Cotswold QNH 1022, wilco, Golf Golf Oscar”

Phew. There’s no way I’d have managed that without reading it verbatim off the crib sheet! The crucial thing I forgot to do until some minutes later, was to actually change the altimeter setting having received the new QNH! Oh well - ninety feet out.

The edge of the Cotswold escarpment approached, looking throughly familiar as we skirted north of Andoversford and over the centre of Cheltenham. It was great to fly over these areas I knew on the ground so well from my late teens and early twenties - and from MS Flight Sim! Gloucester Airport appeared exactly as expected, and as I approached the perimeter I did the four Ts:

Time: noted the time, and calculated ETA at Banbury;

Turn: changing heading about 150 degrees right, I did a teardrop turn to the left;

Talk:

me: “Golf Bravo Tango Golf Oscar in the overhead, turning Banbury”

Gloucester Approach: Golf Golf Oscar, roger, report ten miles north-east”

me: “Roger, Golf Bravo Tango Golf Oscar”

Task: A FREDA check. Noticed that the DI was a bit more out.

I could see that abeam Winchcombe provided a good ten-mile marker, so I looked out for that, distinctively located in a short valley to the north of the our track. Passing over the northern outskirts of Cheltenham, above the racecourse, the Winchcombe valley soon came into sight, and all was well. Abeam Winchcombe, time to talk again and switch back to Oxford:

me: “Golf Bravo Tango Golf Oscar, ten miles to the north-east, freecalling Oxford Approach on 125.325″

Gloucester Approach: “Golf Golf Oscar, roger”

me: click the PTT

<change to Oxford>

me: “Oxford Approach, Golf Bravo Tango Golf Oscar back on frequency”. Might have had something else to say, like we were en route to Banbury, but I can’t remember.

Oxford Approach: “Golf Golf Oscar, roger”

Beyond Winchcombe, the next eight miles or so to the half-way point just before Moreton-in-Marsh were fairly devoid of useful navigational features. I could roughly see that the areas of high ground were in the right place, but there were no distinctive and identifiable roads, railways or towns. So why not get a bit of help locating Oxford? Time for a QDM request: the magnetic bearing to the Oxford ATC station.

me: “Golf Golf Oscar, request QDM, Golf Bravo Tango Golf Oscar”. Have to include the full callsign at the end of the request.

Oxford Approach: “Golf Golf Oscar standby”

We waited a moment…

Oxford Approach: “Golf Golf Oscar, transmit for QDM”

me: “Golf Bravo Tango Golf Oscar, transmitting for QDM, QDM, QDM, Golf Bravo Tango Golf Oscar”. Full callsigns and repetition to make the transmission long enough for the controller to get a good VDF bearing fix.

Oxford Approach: “Golf Golf Oscar, QDM is 119 degrees class Bravo”

me: “QDM 120 degrees class Bravo, Golf Golf Oscar”

So Oxford is 120 degrees magnetic from us (give or take five degrees), in about our two o’clock. Excellent - that makes good sense.

But now, back to dead reckoning. The half-way point of the Gloucester-to-Banbury leg was at the edge of the high ground, before the valley surrounding Moreton, and as we approached the edge I went through the FREDA check. Hmm, the DI had drifted 20 degrees out in barely ten minutes! Suction pressure is fine… maybe it’s a dodgy bearing*. Twiddled it back into place. Now, Moreton should be right on the nose…

It’s not there. In retrospect, this was not surprising! A quick read ground-to-map suggested we were a couple of miles north of track, and that Moreton should in in our one o’clock - and sure enough, there was the disused airfield. A quick correction 40 degrees left for a minute or so, and we were right on track again.

Soon, the factories of Banbury appeared near the horizon. I kept a much closer eye on the DI, correcting it every few minutes. Arriving uneventfully over the town, time for the four Ts:

Time: note the time, calculate Oxford ETA

Turn: south towards Oxford

Talk:

me: “Golf Bravo Tango Golf Oscar overhead Banbury for rejoin, request standard overhead join”

Oxford Approach: “Golf Golf Oscar, roger, standard overhead join, report downwind”

me: “Standard overhead join, wilco, Golf Golf Oscar”

Task: another FREDA check, then continue navigating the last leg. I’m checking the DI more regularly - it really needs to be checked every 3-4 minutes. Soon enough, the chimney at the quarry comes into sight ahead, shortly followed by the runway, and I descend gently to the joining height of 2300ft to commence the manouevre. I must remember to apply carb heat at this point too - any time the power drops below about 2000rpm, really. Descend deadside, level out at circuit height, over the runway, have a good lookout for anything taking off but I see no traffic. Looking out to judge the position of the downwind leg, and make a neat 90 degree turn left to join. Reporting downwind, Tower tells us of traffic in front of us, and we’re number 2 to land. I don’t spot the traffic at first but the instructor does: it’s just turned final. As I later realised, that’s not nearly enough space between us for them to land and vacate the runway before we arrive. So the instructor tells me to extend downwind: we plough on for about another mile or so, before finally turning base and reconfiguring for descent. I kept a little more power on that usual, since the descent is a mile longer than usual. I forgot to put in the final call until slightly late - even at that stage, the leading aircraft hadn’t cleared the runway, and we received a “land after” clearance. Apparently, I’m not allowed to accept that if I’m flying solo, but with an instructor on board it’ll do.

On final, the instructor calls for a full-flap landing, so I keep a little higher for longer than usual. I overdid it, really: ended up aiming at a point nearly a third of the way down the runway, which I wasn’t pleased with. Though looking back, I can’t remember whether I’d actually cut the throttle completely to idle: if not, that would be a reason! Anyway, apart from that, it was a good landing. The best thing was that I didn’t consciously flare: it all just sort of happened automatically. That’s a big deal for me - very pleasing! As we settled downwards from the holdoff, the instructor was telling me to keep pulling further back, and I did but I thought we were still a few feet off the ground… as we gently touched down! I really need to nail that height perception. Not a bad landing at all, though.

* or maybe the examiner had tripped the hidden “make the DI go wonky” button… or was just tweaking the knob behind my back whenever I turned to examine some feature out the left-hand window!