BAe125/Dominie approach speeds

[Razor61]

I know it's a naff question but i was just wondering why the approach speeds (category) are quoted different for each aircraft when essentially i thought they were the same type, or very similar anyway?

Dominie is quoted as Cat B (91-120kts) while the BAe125 is quoted as Cat C (121-140kts). Why is this?

[BEagle]

Because it has a lower approach speed?

[Razor61]

But why have they got different approach speeds when essentially they are the same aircraft. What is different in regards to each aircraft which allows one to approach slower than the other?

[spekesoftly]

The RAF Dominie is based on a very early mark of DH125 from the sixties. As the aircraft type was developed over the years and became the BAe125, its weight increased, probably leading to a slightly higher approach speed.

[ZH875]

Originally Posted by Razor61

But why have they got different approach speeds when essentially they are the same aircraft. What is different in regards to each aircraft which allows one to approach slower than the other?

Are they essentially the same ?:

• DH.125 Series 1 - first production version, 8 built
• DH.125 Series 1A/1B - upgraded Bristol Siddeley Viper 521 (Series 1A) or 522 (Series 1B) engines with 3,090 lbf (13.8 kN) of thrust each
• HS.125 Series 2 - military versions
  • Dominie T.Mk.1, T.Mk.2 - (Rolls Royce Viper 301) navigation trainer for Royal Air Force
  • CC.Mk.1, Mk.2, and Mk.3 - liaison aircraft for Royal Air Force
• HS.125 Series 3 - upgraded engines
• HS.125 Series 400 - upgraded engines
• HS.125 Series 600 - 3 ft 1 in (0.94 m) fuselage stretch to increase capacity to 14 passengers
• HS.125 Series 700 - Honeywell TFE731-3RH turbofan engines with 3,720 lbf (16.6 kN) of thrust each, first flight 19 June 1976
• HS.125 Protector - Series 700-based maritime patrol aircraft with a search radar and cameras
• BAe.125 Series 800 - increased wingspan, streamlined nose, tail fin extension, increased fuel capacity, first corporate jet to feature an EFIS cockpit, upgraded engines, first flight 26 May 1983
• Hawker 800 - BAe.125-800 after 1993

Maybe with a longer fuselage, an increased wingspan and increased fuel capacity, it increases the landing speed.

But as usual I could be talking .

[XV277]

Because they are not the same aircraft and they don't have the same engines?

Garrett fans on the 125s, Viper jets on the Dominie.

Add in the 125s are third generation versions of the design, as against the much earlier Dominies.

[BluntM8]

I thought that traditionally the approach speed of an aircraft was somewhere around 1.3 times the stall speed for the app. configuration?

If that is the case, it would seem apparent that anything which changes the stall speed - such as for example a different wing profile - would affect the approach speed.

Thinking out loud here, could it be that sucessive variants of the HS.125 got wings which were better at high speed/altitude but with less benign stalling characteristics?

Blunty

[Monty77]

Razor

There is no such thing as a naff question in aviation.

There are plenty of examples of those who don't ask questions who end up on cockpit voice recordings just before they die.

Smug replies like those of Beagle are worthless.

Far more instructive and worthy of attention are those who contribute after him to answer your query. They have contributed far more to this thread than the 'What are you, stupid?' attitude that Beagle portrays.

Apparently, he's got something to do with the CAA. Which is nice.

[BEagle]

Monty77, sorry, but there are plenty of so-called 'questions' in modern aviation which are utter bolleaux. Mostly those posed by spotters or MSFS-geeks.

Those who haven't even bothered to do a little research to establish whether an ancient navigator-trainer of the late 1960s is the same aircraft as a corgi-carrier of several decades later don't honestly merit more than a few words....

The only connection I have with the CAA is nothing to do with military aviation. And is all entirely voluntary and unpaid.

[Linedog]

MSFS-geeks.

You play it as well, eh...............???

[Razor61]

Thanks for the replies chaps.
The Dominie and the RAF BAe-125 both fall into the HS-125 Series 2. So i thought both must have the same dimensions or there abouts and do not compare to other series later on.

Sorry for the "utter bolleux" question, just for the record i don't 'play' MSFS or any such "game".

[BEagle]

Please ignore my rude remarks, Razor61 - it'd been One Of Those Days, I'm afraid... Sorry!

Anyway, the Dominie T Mk 1 was an early design; this was substantially upgraded in 1996 after being in service for 31 yeasr. The original comms aircraft were the HS125 CC Mk 1 (civil ser. 400) and the HS125 CC Mk 2 (civil ser. 600).

The present comms version used by 32 TR is the HS125 CC Mk 3, which is a military version of the civil series 700B.

So the Dominie T Mk 1 and HS125 CC Mk 3 are now rather different aircraft.

As an aside, I remember seeing the original DH 89B Dominie in the early 1950s whilst it was parked near 'Westlands Hangar' at RAF Merryfield. I think they were probably the last biplanes in RAF service as they weren't declared obsolete until 1955 - and the Fleet Air Arm still had some in 1961.

Apologies again for being a Grumpy Old Git!

[Razor61]

Thanks Beagle
Like you said, i should have researched more in the first place.

[BANANASBANANAS]

I flew the venerable Dominie from 1987-92 and also did my CAA ATPL type tech exams on it. Then, according to UK CAA, it was an HS125 1B-522.

Funny how certain things stick in your mind. At max take off weight (21000 pounds) V speeds were

V1/VR 121
V2 127
Single Eng Climb Spd 172

Max landing weight (17500 pounds) Vat was exactly 120 Kts - hence it just squeezed into Cat B. I never flew the 'Corgi Carrier' variant but I am guessing that it had either a heavier max landing weight (faster Vat) or some other reason to increase the Vat - hence Cat C.

Usual caveats about age, alcohol and incipient senility apply to all of the above.