Classic British Flight Sim

Thought I'd move this topic here as opposed to sticking to the Harrier thread...

A couple of intersting comparisons in TWR -

Harrier - 1.10
Saturn V - 1.15
Space shuttle - 1.75

And complicating all this (as I usually do) - despite being an electric performer,
Concorde - 0.375 !!

Which shows of course that TWR is not all about 'getting up' as Concorde climbed rather nippily..

Of course a glider with no thrust can climb due to lift/drag ratio.... :roll: ...this is getting out of hand now......

Great subject isn't it Jim. The more you read, the less you know!! That's why I try not to bother.. ignorance is bliss

ATB

DaveB :tab:

Precisely! ;-)

Thinking out aloud again, I wonder if a graph of some sort could be made up giving TWR performance to altitude? (I'm thinking lines from the ground up showing what angle a TWR gives to move a given load at a given speed to a given altitude?) - Unless I am totally wrong (which is not uncommon) this should show up just like a graph?

It would, it would be aircraft specific obviously and would trail off to zero at the service ceiling (depending on you definition of service ceiling, actual mileage may vary). I'm not sure what use it'd be though. Ultimately your TWR is time specific due to engine performance/altitude and fuel/stores consumption, for instance the Saturn V figure would improve as it climbed, whereas the Harrier's gets worse due to the drop of in engine thrust. I'm fairly sure most quoted TWR are for sea level and basically allow a comparison between different aircraft types.

:think:

Well, not much use in the real world, and probably even less use in Flightsim :roll:

It would be handy for a basic climb profile for specific A/C (I think) but I'm not sure it's really feasible to tie in real-world info like that to the way FS is programmed.

I'm not sure about developing a climb profile, unless you're operating in the vertical (i.e. nose pointing skywards) the majority of your lift is coming from the wings/fuselage. Generally climb profiles are based on a constant IAS/Mach No. which will move the aerodynamic surfaces through the air at the optimum speed e.g. the Sea Vixen works on something like 400kts until you hit M0.83 and then M0.83 from there on up. At low speeds I'm assuming this gives the best lift/drag ratio, not sure about what happens when you go transonic but I'd imagine it's no different. There's also the question of whether you're climbing at Vx or Vy, one gives you the best angle of climb and one gives you the best rate of climb (angle is for obstacle clearance i.e. most height gained per unit travelled horizontally and the other is per unit of time i.e. gets you higher faster). A less opaque explanation here.

oops

Why I said 'profile' I'm not sure - I was of course thinking 'going vertical'. Obviously certain other factors come into play with this, but essentially, my thinking was to try and work out (in theory) what the speed bleed off in a vertical climb would be for a given aircraft - and see it it could be replicated in FS to some degree. EG 10 secs at Max power before a stall for example. Trouble is it's fraught with problems such as speed into the nose up, altitude and of course drag etc - I suppose the only real way to do it would be to a) have a list of real figures to compare like with like or b) fly something with no drag at all and just go on power alone.

That should be doable, I don't think the maths would be that hard, just some standard equations of motion. It'd be another way of verifying the thrust and drag values of a model although I'm not sure where you'd get the real world values to compare it to. Anything with a TWR >1 should just keep climbing, anything else would decelerate to a stall.

Some sort of implementation is kicking around at the front of my head right now - I just haven't quite got there with it :brick:

As long as I can come up with a 'standard' I have an idea....

Of course, as you say, anything with +1 TWR should carry on regardless, but, lurking at the back of my mind are various drawbacks to this:

first off, anything other than something with rockets strapped to it seems ludicrous if it carries on climbing (vertically) and of course most TWR figures are (I suspect) quoted on engine performance at sea level - so there is going to be some level of fall off as height is gained (vertically).

What is stumping me at the mo is my inability to trust some M$ performance in default A/C....

Jim, and you are surprised?? ;-)

"It's life Jim but not as we know it."

Chris