HS748 Cruise Speed

Classic British Flight Sim forum.
Support for Maltby/Piper FS models & other Classic British freeware.

Moderators: Guru's, The Ministry

User avatar
DaveB
The Ministry
Posts: 30457
Joined: 17 Jun 2004, 20:46
Location: Pelsall, West Mids, UK
Contact:

Re: HS748 Cruise Speed

Post by DaveB »

Hi Chris :hello:

One thing you can't be accused of is nitpicking and I appreciate the correction ;) It was assumed with the 748 (having had input from ex 748 crew) that the ref speeds were knots as opposed to IAS as there was nothing to suggest a 748 ever went close to the printed speeds in IAS by some way. I admit this never sat comfortably with me as pilots would have to be incredibly clever to convert at a glance IAS to GS and t'other way round. This would be above and beyond the call of duty :lol:
It does seem with the 748 that HS built in a rather grand limit level.. a bit like having a 160mph speedo in a mini.. or not as the case may be.

I stand corrected so Nick.. ignore my previous BLX. Having said that, the 748 will not and as far as I'm aware, did not achieve those speeds IAS ;)

ATB
DaveB B)smk
ImageImage
Old sailors never die.. they just smell that way!

cstorey
Concorde
Concorde
Posts: 1623
Joined: 11 Jul 2004, 19:36
Location: heswall, wirral

Re: HS748 Cruise Speed

Post by cstorey »

Dave, what you said was not BLX , but the limit speeds are in most cases related to the dynamic loads on the airframe of which IAS ( added to by any G load which might be imposed ) is a direct measure . I say in most cases because there are some aeroplanes where a problem e.g tail or aileron flutter necessitated a limit lower than that at which the airframe would not be able to sustain manoeuvring loads. I never tested any large aeroplanes, but on the light aircraft which I did test it was usually necessary to have the aeroplane in a steep dive to get anywhere near Vne which was often something of the order of 80% greater than the cruise speed . The rise in total drag with speed is geometric rather than linear , which accounts for this . I have to say that the Vne test ( which at that time was mandatory for Certification renewal - I don't know whether it still is ) was never my favourite because one always had a sneaking suspicion that something might drop off in the recovery which tended to be high G !

User avatar
DaveB
The Ministry
Posts: 30457
Joined: 17 Jun 2004, 20:46
Location: Pelsall, West Mids, UK
Contact:

Re: HS748 Cruise Speed

Post by DaveB »

:lol: :lol: :lol:

I like the idea of that.. sitting.. quietly perspiring.. waiting for something to fall off :lol: You're MAD! I'll take the motorbike any day ;)

Thanks again for that Chris.. much appreciated :thumbsup:

ATB
DaveB B)smk
ImageImage
Old sailors never die.. they just smell that way!

User avatar
AllanL
Concorde
Concorde
Posts: 813
Joined: 06 Sep 2005, 21:01
Location: Scotland

Re: HS748 Cruise Speed

Post by AllanL »

Just been down sarf of Hadrians Sieve,(well it never kept SWMBO south of it) for a couple of days and took the opportunity to leaf through "The Spitfire Manual 1940" on my way down to Southampton and back. In that was a quote from Teddy Donaldson's 1943 Fighter Pilot's Manual that an approximation for TAS was to add 1mph for every 60mph indicated for every 1,000ft of altitude. So 120mph indicated at 30,000ft would be 120 + (2*30) TAS.

I haven't fired up the sim to check that out.

Of course if you want to get all fancy and use those matelot type speed units, you'll still need a slide rule to figure it out. (Wot's a calculator?)

Tally Ho, toodle pip, Huns in the Sun, :fly: and mine's a pink gin. :party:

SkippyBing
Concorde
Concorde
Posts: 1459
Joined: 30 Aug 2006, 18:21

Re: HS748 Cruise Speed

Post by SkippyBing »

Of course if you want to get all fancy and use those matelot type speed units, you'll still need a slide rule to figure it out. (Wot's a calculator?)
You'll find that equation is unit agnostic. I have had it explained to me but I can't remember off the top of my head how/why it works if I had to hazard a guess I'd say it was working on TAS = IAS + 2%/1000'. 1kt/mph/kph is almost 2% of 60 so it works for a given value of 'works', I'm fairly sure the accuracy falls off with height.
The bonus is any sane person flies at a multiple of 60kts/mph/kph as it makes it relatively simple to calculate ETAs etc. in your head so it's fairly easy to do a TAS calculation at the same time. Or you can fly helicopters and just accept you're going to be late...
Image

User avatar
DaveB
The Ministry
Posts: 30457
Joined: 17 Jun 2004, 20:46
Location: Pelsall, West Mids, UK
Contact:

Re: HS748 Cruise Speed

Post by DaveB »

:lol: :lol: :lol:

ETA expressed as a date rather than a date and time :lol:

ATB
DaveB B)smk
ImageImage
Old sailors never die.. they just smell that way!

User avatar
Garry Russell
The Ministry
Posts: 27180
Joined: 29 Jan 2005, 00:53
Location: On the other side of the wall

Re: HS748 Cruise Speed

Post by Garry Russell »

Like an An-2's radio call..."Overhead Southampton at this time, estimating Hazel tomorrow" 8)
Garry

Image

"In the world of virtual reality things are not always what they seem."

Post Reply