[jhb_airlines] Re: Last night on FPI

  • From: "Bones" <bones@xxxxxxx>
  • To: <jhb_airlines@xxxxxxxxxxxxx>
  • Date: Thu, 29 Sep 2005 16:38:45 +0100

The latter. All it is doing is sensing the localiser signal and turning
towards it until any deviation is corrected. It will do this whether the
wind is 20kts or 90kts (given enough time) and the final heading it settles
on is irrelevant to its logic.
 
The AP is good enough to sense the decreasing and backing wind as you
descend and it will be making constant corrections to actual heading but it
can get a bit stressed in gusty conditions. If the gusts are short and sharp
- nasty for the crew and pax - but not long enough to displace you much from
the centreline then the AP will cope quite well. It is the longer gusts (or
wind shear) that make it work a lot harder.
 
The weather was grim over quite a large area last night. Alex had nasty wind
going into Valley and there was some awful wind shear approaching ROSUN
around FL90 - as Tom and Gerry both found out that hard way. FSMeteo and the
like do quite well in this respect considering they are only getting 30 min
actuals. In real life this is the standard time between reports but it the
weather is changing rapidly (it qualifies for what Met call a Significant
Change) then the reports are made more frequently - in really bad weather
being updated almost constantly. 
 
These Special Reports don't get transmitted. It takes about 15 min for a
normal METAR to reach the big wide world and this is just too slow to
distribute Special Reports. Instead it is the controller who will advise
pilots of the rapidly changing situation - or it may go out on local ATIS if
this is an automatic unit.
 
If a front goes through then the weather can change very quickly indeed -
and this is what happened at Manchester last night. The vis would have
improved over 20 min or so but the METAR's jumped from 3500m to 9999m
instantly. I'd been watching more up to date weather and I was able to tell
Tom in advance that a significant change was on the way. Trouble is that I
couldn't predict when FSMeteo or VATSIM would pick this up and change it in
the sim..
 
bones

-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of FrankTurley@xxxxxxx
Sent: 29 September 2005 08:49
To: jhb_airlines@xxxxxxxxxxxxx
Subject: [jhb_airlines] Last night on FPI



It was a good session last night, I managed 2 hops, Aberdeen to a wet wet
Newcastle, and from there onto a wet, wet, Manchester. On approach to
Manchester the Baron's A/P struggled to hold the ILS in that wind, which
prompted a question for you experts from this humble bean counter -
 
Is the A/P "smart" enough to be proactive in a cross wind and take an
appropriate heading, or does it just react to being off centre and steer to
get back on again?
 
Frank T.   JHB167

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