[jhb_airlines] Re: B747-400

  • From: "bones" <bones@xxxxxxx>
  • To: <jhb_airlines@xxxxxxxxxxxxx>
  • Date: Sun, 9 Dec 2007 17:23:28 -0000

400kts is far too slow for the cruise. That is only about Mach 0.72 when you
should be cruising at Mach 0.84 - roughly 485kts. About the only jet that
flies at 400kts is the BAe146.

Take off should be a little faster than 160kts too. Rotation should be
around 175kts with initial climb at 190kts - increasing to 250kts once gear
and flaps are up. Maintain 250kts to FL100 and then increase to 280-300kts.
At this point start watching the Mach No. as it will begin to rise as you
climb. It will start about Mach 0.57 but once the Mach No hits 0.76 switch
over to Mach Hold and continue to climb at Mach 0.76.

You have to switch to Mach climb because IAS is useless at high levels.
Despite maintaining say 250KIAS your actual speed is increasing with height
and the aircraft doesn't have the power to go faster and maintain a good
climb rate at the same time.

Once at cruising level you increase speed to your normal cruising value,
usually between M0.82 and 0.86.

If you are setting a climb rate on the aircraft then you have to watch that
the autopilot doesn't prioritise this instead of climb speed. If this
happens then the aircraft will try to keep the climb rate going at the
expense of airspeed - a dangerous situation because the speed can decay to
the stall if you don't watch it. Up at FL300 a jet will be lucky to have
half the climb rate at sea level so you should let the aircraft find it's
own rate of climb - just dial in a speed hold and the required height and
leave the climb rate alone. It will initially start at a high value but you
will see if reduce as you get higher (because the aircraft is aiming to
maintain a fixed speed).

I haven't finished the Tutorials page yet - it still needs formatting - but
you should read the two bits on Speed Control. Link is
http://www.homepages.mcb.net/bones/jhb/jhbtutorials.htm but you will have to
search through it as I haven't started an index yet.

bones

-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Franklyn Fisher
Sent: 08 December 2007 22:37
To: jhb_airlines@xxxxxxxxxxxxx
Subject: [jhb_airlines] Re: B747-400


Bones

Rated cruise FL340 at 400kts

TO speed 160. vsi1800
Climbspeed 250 to10000 VSI 1800
FL100-FL200 VSI 1500 speed 280
FL200-FL300 VSI 1200 reducing to 1000.

The 10% noseup is at all flightlevels and speeds.

Have tried altering the C of G and passenger load, with no success.

TO has to be manual to hold max 10% climb rate with 20 flaps.

Auto pilot heading and climb hold is engaged above 1000 and gear retracted,
flaps retracted above 5000, this to hold a stable climb.

After turn to WP, FSC engaged. (with all other AC, I can engage full auto,
from liftoff, with no problems)

As I approach FL300 and and before starting to increase speed to cruise, it
then starts to go into a noseup stall very rapidly. And it is then
uncontrolable. Time to cruise level, approx 30 minutes.

Will have a go with the other Boeing to see if it is the same, no problem
witht the other default aircraft .

I only have default AC, so cannot use another long range craft.

I suppose I should purchase a PMDG craft for the job.

Frank F


----- Original Message -----
From: "bones" <bones@xxxxxxx>
To: <jhb_airlines@xxxxxxxxxxxxx>
Sent: Saturday, December 08, 2007 9:14 PM
Subject: [jhb_airlines] Re: B747-400


> It sounds like you are flying too slowly and getting on the back of
> the
> drag
> curve. What sort of speed are you using for the climb?
>
> Also make sure you don't set a specific rate of climb for any jet.
> It's
> fine
> setting 1800fpm at sea level but if the autopilot is trying to maintain
> that
> rate of climb at higher levels it can only do so by losing airspeed. The
> autopilot should be set to maintain a speed value instead - which it will
> maintain as you get higher by automatically reducing the rate of climb.
>
> This is the trouble with autopilots - you can direct them to do the
> wrong thing very easily. In FS4 we had no option with the climb - if
> you dialled in a height and speed it would always give priority to
> rate of climb. The result was that the higher you got the more the
> aircraft lost speed until it eventually stalled. Later sim versions
> were more intelligent and rate of climb is no longer the default value
> driving the aircraft - but you can still set the aircraft to do this.
>
> The 747 should be able to climb up to FL310 without any problem but if
> heavy
> with fuel it may need to fly for an hour or so before stepping up the
> FL350
> and (eventually) FL390.
>
> bones
>
> -----Original Message-----
> From: jhb_airlines-bounce@xxxxxxxxxxxxx
> [mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of franklyn
> fisher
> Sent: 08 December 2007 15:23
> To: jhb_airlines@xxxxxxxxxxxxx
> Subject: [jhb_airlines] B747-400
>
>
> Help please
>
> I am trying to set up a trans-atlantic flight using the default
> B747-400 FSX.
>
> After numerous takeoffs, I have found the way to do a smooth takeoff
> and climb, before engaging FSC.
>
> However, dispite modding the config file, am unable the get the AC to
> cruise
>
> at less than 10% nose up.
>
> Have found that stepping up to cruise (with a step down in the VSI) is
> required. But once at FL300, any futher increase to the stated cruise,
> results in the nose going up, speed rapidly dropping to zero, and am
> on the deck in seconds.
>
> Very frustating.
>
> The CRJ700 wont make the trip in one, without midair refuel..
>
> Either I am not doing something right, or M$ has not done their
> homework. this is supposed to be their own tried and tested.
>
> Frank F
>
>
>
>
>
>
>
>
> --
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> 08/12/2007 11:59
>
>





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