I was on the route of WSSS-EGLL (Singapore to London) when during approach the QNH for London setting was locked out meaning that i had to approach off a QNH of 1013.2 the standard datum above FL60 (6000 feet in London), meaning just a straight visual approach on QFE.
This time though the Cloud was 7/8-8/8 meaning an autoland Cat 3 approach was what was required;Aerowinx randomly set this up. So what to do?
QNH at London was 1007, so 1013-1007+6 (x20feet) pressure altitude = 120 feet plus the elvation of London above mean sea level which is 83feet and you need to guide the aircraft through a further 203 feet before touchdown with no visual references. So what happended?
Well on an autoland approach monitor the altitude as it s sank below 0 feet, ignoring "sink rate/go around" audio signals, watching the altitude to -156 feet with hand on the throttle in case of an intervention. The wonderful 747-400 settled smoothly on the runway with normal deceleration although i insisted on early reverse thrust & the speed brake coming up early.
Of coures the reverse thrust was closed at 60knots accoding to Stanbdard Operating Procedures to stop foreign matter getting into the engine & applying moderate braking down to tiller speed of 20 knots. At this point there we were perfectly aligned with the runway lights. So what did I learn?
1. I`ve never had to do a landing on Standard datum of 1013.2 so the software can create some interesting realistic situations.
2. The fact that I couldn`t see the ground plus an auto land required constant monitoring of the PFD (Primary Flight Director) just like in real life.
3. Be prepared to do some maths and physics calculations no matter what phase of flight you`re currently in. i was trying to work out how far reverse was the aeroplane mean chord but unsuccessfully.
Have a great weekend wherever you are flying to and may all your Autolandings be good ones.
Till next time from Oz,
Neil
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