HS 748 Performance

[Nigel H-J]

Hi all, OK, appreciate that I am becoming a bit of a nuisance with my questions regarding the 748 but refering to my previous post just would like to know whether the performance figures below are normal so that I can stop wondering and get on flying it.

As a reference with the FS9 version flying at 14,000ft I was able to maintain 202kts with around 85% power.

FSX version:-

14,000ft ASI 195kts max at 100% power setting

At 86% throttle setting ASI 188kts with 14,175 RPM Fuel flow 910lbs per hour

8,000ft 198kts at 85% throttle setting fuel flow 1074lbs

6,000ft 202kts at 86% throttle setting fuel flow 1145lbs

Higher the altitude the less fuel burn there is. As for the airspeed being lower with increased height has me somewhat puzzled as this never happened with the FS9 version as far as I can remember.

If any-one has the time and patience to answer or try this out and let me know I would be very grateful!! Even if I have to wait until back at work on Monday!!

Kind regards
Nigel.

[DaveB]

Hi Nige

I don't think I'm gonna even try to answer all of that so you may have to wait until Monday

A couple of points though. Airspeed will drop as altitude increases as a matter of course no matter if this is FS9, FSX or RW as far as I know. As the air gets thinner.. there's less for the props to 'bite' on.

I don't really remember what the throttle settings were.. only that you give it full chat for takeoff and when established in a positive climb (or 5mins max).. throttle back to 12200 and remain there for the remainder of the climb and cruise. You take whatever airspeed you can get depending on headwind e t c.

It is not uncommon for FS9 models to give slightly less performance in FSX. Exactly the same happened with FS8 models when dragged into FS9 and probably with every other incarnation before.

There! I doubt it will satisfy your needs but that's all you'll be getting tonight

ATB
DaveB

[Nigel H-J]

There! I doubt it will satisfy your needs but that's all you'll be getting tonight

Thanks Dave, I don't even think I will get a full answer by Monday either!!

With the 748 I usually keep down below 8,000ft to give the passengers a good view of the countryside....me included!!

Just came across this variation of speed when flying higher and just wanted to know if this is normal with the HS748.

May remain one of lifes' mysteries!!

Many thanks and kind regards

Nigel.

[Viscount Cornbank]

Hi Nigel.

The FSX figures sound about right at 14200RPM. There will also be a lower power output when the fuel trim is less than 100%. Remember the airspeed indicator is showing indicated airspeed not true airspeed, the difference between the two increasing with increased altitude.

cheers

Fraser

[PaulC]

The ASI reading will decrease with altitude as it's the Indicated Air Speed.
You may know this, so tell me if I'm teaching anyone (particularly Granny) to suck eggs, but in simple terms;

As altitude increases the air becomes thinner and pressure decreases. This gives less air to press against the workings of the airspeed indicator, hence it reads lower. At M2.00 and 60000', Concorde's ASI read about 300, despite the fact it was racking on at 1500 knots!

If you work out the True Airspeed (TAS), you'll find it increases.

Rough calcumalarions on my gabbleaddictum say that at 14000' with an IAS of 195, the TAS is 245.
At 6000, 202IAS gives a TAS of 219. This is assuming standard pressures etc.

So in actual fact, you're picking up speed flying higher.

You could always check this if you can pull up the default GPS ( I hate it too) and look at your ground speed.

Hope this helps.

Paul

[NigelC]

Rough rule of thumb is IAS to TAS = Add 2% per 1000ft

IAS = 188
Alt 14000 so 14 x 2% = 28%

Gives 188 + 52 = 240kts, looks pretty much spot on for a Budgie to me

[WhisperJet]

It is not uncommon for FS9 models to give slightly less performance in FSX.

Okay, so I'll stay with FS9.



Cheers,

Nick

[DaveB]

That was easy Nick. Something tells me you didn't need much convincing

'Tis true though. Exactly the same happened with 2002-2004. I'd been running the Trident2 solid for around a week getting the fuelburn to where it needed to be (UK-Cyprus run) and prior to release, 2004 was released and by magic.. the Trident wouldn't reach Cyprus in the new sim Same applied to the HP42 I was testing at the time

ATB
DaveB

[Nigel H-J]

Hi Chaps, many thanks for all your replies however!! Guess what!! I came across a 2013 manual written by Fraser and it says what you all wrote. Sorry chaps, going to have to read the manuals in future.

Many thanks again

Kind regards
Nigel.
:

[DaveB]

I came across a 2013 manual written by Fraser...

I'm sure he'll be thrilled



ATB
DaveB