[jhb_airlines] Re: Article

  • From: "Bones" <bones@xxxxxxx>
  • To: <jhb_airlines@xxxxxxxxxxxxx>
  • Date: Sat, 27 Nov 2004 18:35:34 -0000

You are sort of right and wrong..

The ILS isn't really dependent on your altimeter setting as the =
glideslope
will captured and flown down correctly whatever your altimeter is set =
to. An
incorrect QNH may do nothing more than affect the point at which you
intercept the glidepath.

If pilots are plugged in to FPI then I would now assume that they will =
also
be getting the weather from the FPI server as well as the controllers. =
If
not then FPI are assuming that most pilots will be flying with FSMeteo =
or
ActiveSky - in which case their QNH values will tie up with the =
controllers
data.

Again, if FPI isn't pushing out weather data and pilots can actually =
choose
their weather, then it does become a more complex issue because their
pressure settings will be based on what their FS setup has set and any
controller issued QNH will have to be ignored. I would suggest the =
following
(if weather is not set by FPI):

If you use any real weather data then follow the standard procedures for
both flight levels and an QNH issued by ATC. Taxi out on QNH and when
climbing through the Transition Level change over to 1013.2 (29.92). On
descent stay on 1013.2 until the controller clears you down to an =
altitude
rather than a flight level. Once you are given an altitude to descent to
change to QNH and leave this on for the rest of the flight. In other =
words
pay a bit of attention to the wording of the controllers instructions.

If you have set your own weather for an FPI session then do exactly the =
same
as above but if the controller gives you a QNH don't set this. Instead =
just
press the B key on your keyboard. This will set the altimeter to the =
local
QNH for the area you are in and your heights should be correct in =
relation
to height above sea level.

The only disadvantage of using user defined weather is that the QNH may =
be
quite different to the real weather pressure. This may show your height
incorrectly on the controller's screen as the radar tube will be =
calibrated
to the controller's QNH. I don't know what happens if you fly near other
aircraft in FPI though - you may well display at the wrong height to =
them
too..

Kevin - if you load real weather and then, as you sit on the apron, you
press the B key your altimeter should show the airfield height AMSL (the
local QNH value). If your system stays at 29.92 then summat's wrong..

bones



-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Kevin Townsend
Sent: 27 November 2004 17:13
To: jhb_airlines@xxxxxxxxxxxxx
Subject: [jhb_airlines] Re: Article=20


As a new controller on FPI - some of you may have contacted me as EGLF=20
Tower, I conclude that although QNH within FPI is derived from actual=20
Metardata and I pass it on religiously (and expect a readback) anyone=20
attempting an ILS approach with anything other than STD (1013 or 29.92 ) =

will result in an overshoot or land short (crash), distance relative to =
the=20
difference in pressure setting!
FS9 I believe has no mechanism to realistically adjust airport height to =

altimeter settings. (Maybe this should be on the wish list for FS10?)

Am I wrong?

Kev

At 00:52 11/25/2004, you wrote:
>Ah.. This is something different. (
>
>The Missed Approach Procedure is always based on QNH. For those of us =
=3D=20
>who fly an approach using QFE it means we check on final that one=20
>altimeter =3D is
>set to QFE and the standby altimeter is set to QNH. On starting the =3D
>missed
>approach we therefore use the standby for initial height guidance until =
=3D
>we
>get to the checklist item and then switch the primary altimeter to QNH =
=3D
>also.
>
>In this context it simply means that if the crew choose to use QFE for=20
>landing then one dial stays on QNH. It doesn't suggest that QFE is=20
>mandatory. I can add to that too and say that ATC do not pass QFE=20
>unless specifically requested. Nor is it found on an ATIS broadcast -=20
>simply because most weather is airfield related but QFE is specific to=20
>each =3D runway (based on threshold elevation).
>
>Looking at an old Aerad plate before I see the DH was shown in both =3D =

>height AMSL and AAL so I'm thinking the QNH guys use the former and the =

>QFE =3D guys
>use the latter..
>
>bones
>
>-----Original Message-----
>From: jhb_airlines-bounce@xxxxxxxxxxxxx=20
>[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of gwinsk@xxxxxxx
>Sent: 24 November 2004 22:01
>To: jhb_airlines@xxxxxxxxxxxxx
>Subject: [jhb_airlines] Re: Article=3D20
>
>
>Perhaps a clue lies in a recent accident report. A flight doing a=20
>missed approach ran into=3D20 high ground. It was found that both=20
>altimeters were on QFE "Not having =3D been
>reset after=3D20
>the overshoot". Apparently one is supposed to be set on QNH, if the =3D
>other
>has been set=3D20
>to QFE, which more or less confirms they have a decision height QFE on =
=3D
>one=3D20
>instrument?
>
>Gerry Winskill
>gwinsk@xxxxxxx
>
>
>
>On 24 Nov 2004 at 19:33, Bones wrote:
>
> > Astute question. I was going to write back and say "yes" but then=20
> >I=3D20  had =3D3D to pause and think for a bit.=3D3D20 =3D20
> > You see, the UK airlines almost all used QFE up until a few years =
ago=3D20
> > =3D3D and then most migrated to the US policy of remaining on QNH.  =
If=3D20
> > landing QNH then ATC don't pass the QFE value - and so Decision =
Height =3D
>
> > can't be QFE related. Or so the logic told me, but it also=20
> >sounded=3D20  wrong. =3D20
> > Looking up the DH of 27L at Heathrow gives a value of 250ft and this =
=3D
>=3D3D=3D20
> > must be a QFE value (height above airfield) as Heathrow is about=20
> > 202ft =3D
>
> > AMSL. =3D3D That would mean a DH of 452ft QNH.
> >=3D20
> > I had two thoughts here. One was that pilots add their DH to the=20
> >=3D3D=3D20  airfield elevation and the other was that they set DH on =
the=20
> >Rad Alt.=3D20  In fact it seemed logical that the latter was the=20
> >sensible route but=3D20  then I worried about sloping ground =
affecting=20
> >Rad Alt readings. I had=3D20  to resort to a =3D3D web search and =
found=20
> >evidence at=3D20 =20
> >http://av-info.faa.gov/terps/Policies1/TIL00005Aatt.PDF that DH is=20
> >not =3D
>
> > =3D3D used with the Rad Alt unless the pilot knows the height of=20
> >the=3D20  terrain at the =3D3D DH location and adjusts for the =
difference=20
> >between=3D20  threshold elevation. =3D20
> > I conclude, for the moment, that DH is indeed set on the altimeter =
and =3D
>
> > =3D3D that the crews must have a QNH as well as QFE value on their =
=3D
>plates=3D20
> > to set. =3D3D I'll have to look further as a read through the UK=20
> > AIP=3D20 hasn't provided any clues.. Just accept that the CAA plates =

> > avoid any=3D20 reference to DH or MDH =3D3D and therefore aren't =
quite=20
> > as good as =3D
>getting=3D20
> > Aerad or Jepp plates..
> >=3D20
> >=3D20
> > bones
> >=3D20
> >=3D20
> > -----Original Message-----
> > From: jhb_airlines-bounce@xxxxxxxxxxxxx=3D20
> > [mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of=20
> >gwinsk@xxxxxxx
> > Sent: 24 November 2004 17:09 To: jhb_airlines@xxxxxxxxxxxxx =
Subject:=3D20
> > [jhb_airlines] Re: Article=3D3D20
> >=3D20
> >=3D20
> > Presumably Decision Height relies on QFE? If memory serves me right, =
=3D
>=3D3D=3D20
> > We're only=3D3D20 given QNH by FPI controllers........
> >=3D20
> > Gerry Winskill
> > gwinsk@xxxxxxx
> >=3D20
> >=3D20
> >=3D20
> >=3D20
> > On 24 Nov 2004 at 5:10, Bones wrote:
> >=3D20
> > > Panel
> > > I honestly don't know what the cockpit is from on that first photo =

> > >=3D20 but I have a sneaking suspicion it's the much modified NASA=20
> > >Boeing =3D20 737. =3D3D20  MCP
> > > Yep, MCP is indeed Master Control Panel. You can take this as the
> > > block =3D3D3D of switches on the default FS aircraft covering the =
HDG, =3D
>=3D3D
> > ALT,=3D3D20
> > > Speed, VS, =3D3D3D APR, BC buttons etc or as the Go Flight MCP =
unit.=20
> > > =3D
>As=3D20
> > > =3D3D
> > most=3D3D20
> > > add on aircraft =3D3D3D have a similar bank covering these =
functions=20
> > > - =3D
>
> > > and =3D3D
> >=3D20
> > > the article was beginning to dive into slightly deeper waters -=20
> > > it=3D20 was =3D3D
> >=3D20
> > > necessary to start using more exact terminology to avoid =3D20=20
> > >generating=3D3D20 confusion. =3D3D20  Speed control
> > > Speed behaviour in FS is pretty accurate and you hit the same
> > > problem =3D3D3D found in the real world. In fact slowing down in =
the
> > > descent =3D3D
> > becomes=3D3D20
> > > a problem even down to GA levels once you get a fairly =3D20=20
> > >streamlined=3D3D20 aircraft. A Cherokee or C172 does not have any =
=3D20=20
> > >problem but move up to=3D3D20 the PA24 =3D3D3D Comanche or PA31 =
Navajo=20
> > >=3D
>and =3D20
> > >you get a shock. =3D3D20
> > > The basic dilemma is that sleek aircraft cannot descend and slow =20
> > >down at =3D3D3D the same time. Even with much reduced throttle many =
=20
> > >aircraft=3D3D20 remain close to cruise speed when descending and so =
=3D
>you
> > > are in the=3D3D20 trap of foregoing one =3D3D3D for the other - it =
is=20
> > > =3D
>either
> > > rate of descent =3D3D
> >=3D20
> > > or airspeed that you opt for. =3D3D3D You can't do both. =3D3D20
> > > The trick is to ignore the book figures for descent rate for the =
=3D
>=3D3D3D =3D20
> > >aircraft and use something less. In the PA31 we used a 500 fpm =
=3D20=20
> > >descent =3D3D
> >=3D20
> > > rate at =3D3D3D 180kts as this is easy to calculate. If up at =
FL100=20
> > > it =3D
>=3D3D
> > would=3D3D20
> > > take 20 min to =3D3D3D descend to sea level and at 3nm per minute=20
> > > this =3D
>=3D3D
> > would=3D3D20
> > > mean starting down some =3D3D3D 60nm from destination. Also, at =
=3D
>500fpm,=3D20
> > > we =3D3D
> >=3D20
> > > had a bit of flexibility as we =3D3D3D could still slow down a bit =

> > > or  =3D
>
> > >we=3D3D20 could increase ROD. =3D3D20
> > > For the bigger jets I'd ignore the default 1800 fpm rate set by=20
> > >the  autopilot and use 1500 fpm. You would have to check each=20
> > >aircraft  to=3D3D20 see what ROD they use so the above is just a=20
> > >guideline. At  the=3D3D20 shallower =3D3D3D descent rate the=20
> > >autothrottle would =3D
>probably
> > > have a bit =3D3D
> > of=3D3D20
> > > power on and so you'd have a small degree of control over=20
> > > speed=3D3D20 =3D
>
> > > settings. An example is one of =3D3D3D the default aircraft (747 =
or=20
> > > =3D
>737
> > > - =3D3D
> > I=3D3D20
> > > can't recall) that won't peg at 250 kts during normal=20
> > > autopilot=3D3D20 =3D
>
> > > descent but stays up nearer 270/280kts. Reducing =3D3D3D ROD will =
=3D
>bring=3D20
> > > =3D3D
> > the=3D3D20
> > > aircraft back under the autothrottle envelope.
> > >=3D3D20
> > > Admittedly this will entail a longer descent profile and so you=20
> > >=3D20 should =3D3D3D plan for this. Alternatively use FSNav to =
compute=20
> > >the =3D
>top =3D20
> > >of =3D3D
> > descent
> > > - but =3D3D3D make sure you change the ROD in the aircraft's =3D
>profile=3D3D20 =3D20
> > >first.=3D3D3D20 =3D3D20
> > > Speed brake is the ultimate option and should be used if ATC ask=20
> > >for  an expedited descent or if you know you've miscalculated the=20
> > >bottom  of =3D3D
> >=3D20
> > > =3D3D3D descent point. Flaps are generally no help but again =
this=3D20=20
> > > varies=3D3D20 with aircraft =3D3D3D type - I think the 747 has a =
high=20
> > > =3D
>figure=3D20
> > > of 270kts =3D3D
> > for=3D3D20
> > > first stage setting =3D3D3D and there are probably others too. =
=3D3D20=20
> > > Spoilers I've had a look at both the PMDG 737 and IFDG A320 air=20
> > > files and it is possible the spoiler drag is in Section 1101=20
> > > <36h>. I'd play with this =3D3D
> >=3D20
> > > carefully though as the former only has a value of 15 in that box=20
> > >=3D20 =3D3D3D=3D3D20 whereas the latter has 123! The default 737 is =
even=20
> > >higher =3D
>at =3D20
> > >261.. =3D3D20
> > > Missed Approach Procedure and Decision Height/Minimum Descent=20
> > >Height  These used to be shown on AIP approach plates a while back=20
> > >but  they=3D3D20 have been removed as they are now considered =
company=20
> > >=3D
>minima.
> > > The=3D3D20 Jepp/Aerad charts still give the data (airlines then=20
> > > factor this for=3D3D20 local use) but =3D3D3D you don't have to =
resort=20
> > > to =3D
>searching
> > > these out. I=3D3D20 will explain..
> > >=3D3D20
> > > A few years ago the CAA was criticised for not stipulating minima  =

> > >=3D3D3D because this allowed non company aircraft (business or=20
> > >private
> > > aircraft) to =3D3D3D approach in far worse conditions than the =3D
>airlines
> > > or =3D3D
> >=3D20
> > > charter aircraft (which =3D3D3D were legally bound to publish=20
> > > minima=3D20 for=3D3D20 their pilots). A lot of other =3D3D3D =
countries=20
> > > had already=3D20 produced State =3D3D
> >=3D20
> > > Operating Minima and the CAA eventually did =3D3D3D the same. =
=3D3D20=20
> > > To dig this out requires a bit more digging into the AIP. Ignore=20
> > > the approach charts and open up the Textual Data page for the=20
> > > airfield. =3D3D
> > =3D3D3D=3D3D20
> > > Scroll down to Section 2.22 Flight Procedures and look for =
sub=3D20=20
> > > section =3D3D
> >=3D20
> > > 6 - Aerodrome Operating Minima for Non Public Transport Flights.=20
> > >=3D20 This=3D3D20 should give you the basic data you can go on. =
=3D3D20 =20
> > >For example at EGNS it gives for the ILS/DME 26 approach a DH of =20
> > >250ft =3D3D3D and minima of 700m RVR. If the glidepath is U/S and =
you =20
> > >are flying =3D3D
> >=3D20
> > > the Localiser/DME approach the DH is raised to 400ft and RVR =
to=3D20=20
> > > 1200m. =3D3D
> >=3D20
> > > A =3D3D3D radar approach (SRA) has a much higher limit - 600ft - =
=3D
>because=3D20
> > > =3D3D
> > it=3D3D20
> > > is deemed a =3D3D3D non precision approach, as are NDB or VOR =3D
>letdowns.=3D20
> > > If =3D3D
> >=3D20
> > > you look at Heathrow =3D3D3D (and almost all other airports) the =
=3D
>limits=3D20
> > > =3D3D
> > are=3D3D20
> > > much the same - 250ft for an =3D3D3D ILS, 400ft for a Loc/DME and =
=3D
>600ft=3D20
> > > =3D3D
> > for=3D3D20
> > > most others.
> > >=3D3D20
> > > The Missed Approach Point is shown on the approach plate but not=20
> > >for =3D
>=3D20
> > >an =3D3D3D ILS approach as it is redundant. This goes back to =3D20 =

> > >definitions =3D3D
> > so=3D3D20
> > > bear with =3D3D3D me whilst I explain again.
> > >=3D3D20
> > > An ILS is defined as a Precision Approach. Because of this the=20
> > >=3D3D3D =3D
>=3D20
> > >terminology is slightly different in that the point at which=20
> > >the=3D3D20 =3D
>=3D20
> > >approach is =3D3D3D terminated is called the Decision Height. Non =
=3D3D
> > Precision=3D3D20
> > > Approaches (VOR, NDB and Localiser only) use a different point =
=3D20=20
> > >called=3D3D20 the Minimum Descent Point. There are subtle=20
> > >differences.=3D20 =3D3D20  With the ILS the aircraft is allowed to=20
> > >descend to the DH=3D20 (usually  250 =3D3D3D ft) and, if the crew =
don't=20
> > >see the runway or=3D20 approach lights  they=3D3D20 HAVE to execute =
a=20
> > >missed approach. In =3D
>other=3D20
> > >words there  isn't a MAPt=3D3D20 for this procedure because it is=20
> > >the=3D20 same point as  the DH. =3D3D20
> > > For Non Precision Approaches the aircraft can fly down to the MDH
> > > but =3D3D3D then it is allowed to level off and remain at the MDH =
=3D
>until
> > > it =3D3D
> > gets=3D3D20
> > > to the =3D3D3D MAPt - only then does it go around. So, a MAPt=20
> > > (I'm=3D20 adding=3D3D20 the little T because =3D3D3D the charts =
now show=20
> > > it as =3D
>MAPt=3D20
> > > rather than =3D3D
> > MAP)=3D3D20
> > > is only necessary and shown =3D3D3D for non precision approaches. =
=3D
>=3D3D20
> > > If you are wondering about the oddity of the non precision=20
> > > approach then =3D3D3D let me explain. In the old days prior to DME =
a=20
> > > VOR or NDB=3D3D20 approach was flown =3D3D3D on timings only - =
pilots=20
> > > didn't =3D
>have
> > > an =3D3D
> > distance=3D3D20
> > > information to show how =3D3D3D close they were to touchdown.=20
> > > This=3D20 still=3D3D20 applies to airfields without DME too =
=3D3D3D - it=20
> > > isn't a=3D20 historical issue =3D3D
> >=3D20
> > > (look up the NDB plate for Cranfield).=3D3D3D20
> > >=3D3D20
> > > The approach procedure was based on flying over the beacon at a=20
> > >set  =3D
>
> > >=3D3D
> > =3D3D3D
> > > height and flying outbound for several minutes - the exact =3D
>timing=3D3D20=3D20
> > > depending on =3D3D3D your approach speed. You then turned inbound =
=3D
>and=3D3D20=3D20
> > > descended to the MDH. If you =3D3D3D got it right this would =
almost=20
> > > be =3D
>=3D3D
> > like=3D3D20
> > > an ILS and you would reach MDH fairly close to the runway.=20
> > > However,=3D20 if =3D3D
> >=3D20
> > > the wind was strong or unpredictable it could muck up the=20
> > > descent=3D20 and=3D3D20 you could easily find yourself at MDH with =

> > > =3D3D3D a mile of =3D
>so=3D20
> > > to go -=3D3D20 hence the need to stay at that height until the =
MAPt.=20
> > > =3D
>=3D3D3D=3D20
> > > You could =3D3D
> > play=3D3D20
> > > safe and reduce the descent rate to stop this happening but=20
> > > =3D3D3D=3D20 you=3D3D20 could then be faced with the opposite =
problem in=20
> > > that you=3D20 might still=3D3D20 be coming down to MDH as the =
airfield=20
> > > appeared in =3D
>the=3D20
> > > murk below you - =3D3D
> >=3D20
> > > with =3D3D3D you too high to effect a landing.
> > >=3D3D20
> > > So the MDH rule still applies to non precision approaches even =
=3D20=20
> > >though we have the luxury of DME to show us exactly how close we=20
> > >are  =3D
>
> > >to an =3D3D
> > =3D3D3D=3D3D20
> > > airfield. This makes such approaches much more safe and=20
> > > accurate=3D20 and=3D3D20 you would =3D3D3D think the DH rule could =
be=20
> > > applied to them =3D
>but=3D20
> > > there is=3D3D20 one more factor for keeping the MDH. Autopilots=20
> > > can=3D20 track and ILS and=3D3D20 they can be programmed =3D3D3D =
to flag=20
> > > the DH =3D
>and=3D20
> > > alert the pilots to land =3D3D
> >=3D20
> > > or go around. This still can't =3D3D3D be done with a non =3D
>precision=3D3D20 =3D20
> > >approach. All you can do with a NPA is use the autopilot to fly =
=3D20=20
> > >the=3D3D20 correct inbound heading but it can't be given any =
descent=20
> > >=3D20 guidance.=3D3D20 Therefore you just dial up the MDH and let =
it=20
> > >take you =3D
>=3D20
> > >down to that=3D3D20 height. =3D3D20
> > > I think I'd better add that to the page...
> > >=3D3D20
> > > bones
> > >=3D3D20
> > > -----Original Message-----
> > > From: jhb_airlines-bounce@xxxxxxxxxxxxx =20
> > >[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of =20
> > >gwinsk@xxxxxxx Sent: 23 November 2004 14:08 To: =20
> > >jhb_airlines@xxxxxxxxxxxxx Subject:=3D3D20 [jhb_airlines] Re: =20
> > >Article=3D3D3D20 =3D3D20
> > >=3D3D20
> > > John,
> > > Having read and re read the "Article", and learned a lot from it,
> > > may I =3D3D3D ask a few=3D3D3D20 questions?
> > >=3D3D20
> > > Very important. What's the aircraft featured in the first
> > > photograph? =3D3D3D I'm thrown by the=3D3D3D20 presence of what =
look =3D
>like
> > > sidesticks, on =3D3D
> > to of=3D3D20
> > > a central control =3D3D3D column?
> > >=3D3D20
> > > What is the Autopilot MCP? I know the answer is going to be =
=3D3D3D=20
> > >=3D20 embarrasingly obvious? Is=3D3D3D20 it Master Control Panel? =
=3D3D20 =20
> > >Not in the article but arising from it. I find that some of the FS  =

> > >jets =3D3D3D are reluctant to slow,=3D3D3D20 entailing a need to =
start =20
> > >the=3D3D20 decelleration way ahead of the 10,000' =3D3D3D point, or =
any =20
> > >other=3D3D3D20 =3D3D
> > speed=3D3D20
> > > control point. If the first stage of flaps can't be deployed=3D20=20
> > > until=3D3D20 down to 220kias,=3D3D3D20 then that just leaves the =
=3D
>spoilers.=3D20
> > > On the IFSDG =3D3D
> >=3D20
> > > A320, the braking =3D3D3D effect of the spoilers=3D3D3D20 is =
minimal.=20
> > > =3D
>I've =3D3D
> > looked=3D3D20
> > > through Aircraft.cfg and used AirEdit on the =3D3D3D .air file, =
but=20
> > >=3D20 can't=3D3D20 find=3D3D3D20 a way of increasing the spoilers' =
drag.=20
> > >Any =3D20 ideas? =3D3D20  I was sure I'd preserved your words of =
wisdom=20
> > >on the subject but  can't, =3D3D3D now, find them.=3D3D3D20 The =
info=20
> > >I'm seeking is on =3D
>Decision
> > > =3D3D
> > Height=3D3D20
> > > and MAP differences and determination.=3D3D3D20
> > >=3D3D20
> > > Something else is sure to hit me, so I may be back. Meanwhile, off =

> > >=3D20 to =3D3D3D see whether=3D3D3D20 Werner Schott's Checklists =
can be=20
> > >chopped =3D
>=3D20
> > >down =3D3D
> > and=3D3D20
> > > stuck onto file card. =3D3D3D I'm
> > >=3D3D20
> > > disappearing under paper and can't find the thrust lever! =3D3D20  =

> > >Gerry Winskill  gwinsk@xxxxxxx
> > >=3D3D20
> > >=3D3D20
> > >=3D3D20
> > >=3D3D20
> >=3D20
> >=3D20
> >=3D20
> >=3D20





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