strongest wing tip vortices when slow, clean and heavy. BUT WHY?

[Lightning Mate]

Sir Richard,

"Heavier aircraft (of the same type) glide further than lighter aircraft as they start with a higher total energy."

Not true I'm afraid.

Best glide range is achieved at the optimum lift/drag ratio. The heavier aeroplane will maintain exactly the same lift/drag ratio as the lighter one provided that speed is increased.

Therefore, providing the aeroplane is flown at the correct speed for the weight, glide range will not be affected by weight.

[John Farley]

Lightning Mate

I would agree with your comments providing you prefaced them with "in still air".

Competition glider pilots stuff in loads of ballast when flying into a head wind to up their glide speed and increase their range (think headwind case equal to normal light weight glide speed when you would have zero range)

JF

[Lightning Mate]

Good call John - maybe I should have gone to Specsavers....

[Pugilistic Animus]

Beautiful
There'll never be another Concorde
PA

[HarryMann]

I just love that lower picture, HM! So illustrative. Any idea what alpha that is, and what the 'white' ?vortex? is which appears to start 'nowhere'?

Being well out of touch with modern aerodynamics like the ogive, has the 'stall' been re-defined for these shapes? Obviously there is no clear point where flow 'separates' since it is pretty well 'separated' at most angles and the classic 'nose-drop' and sudden onset of sink rate are no longer there. Do you know what the trigger is for the ultimate breakdown of the 'attached' vortex?

BOAC

It looks like the white is a trace started from a smoke cannister or similar, set some distance above the wing surface, presumably to show the flow in that plane, which if so, looks interesting (caused by the vortex picking it up being much expanded by then)

I think one way of defining a 'stall ' for these types of wings, could be simply maximum Cl, attainable, regardless of drag and thus thrust required for stable unaccelerated flight.i.e. A lot!

Another 'limit' might be buffeting 'G' - Concorde would shake about at lower speeds noticeably, I believe at anything much below 250 kts, and buffet badly during landing flare - have never flown on it, but think that pax were told/warned not to worry

PS. Green smoke is indicating fuselage vortices, as these can upset things quite a bit, apparently.

The ideal shape for M 2.0 cruise is a straight taper leading edge, with span roughly half the root chord. This is not ideal for subsonic flow, flaring the wing into the fuselage and reducing sweep at the tip creating that ogive or gothic shape, and then some further wing/body refinements made enormous difference, and much work went into the engine nacelle interaction with the wing's flow too, let alone the marvel of the whole intake system (26 feet long?). Reducing trim drag was a very importnat engieering goal, and together with fore/aft fuel management, gave the range required.

[Pugilistic Animus]

does anybody have some stats on the photo of the streamline ilike BOAC had orginally asked i.e AoA, Reynold's number, mach number

any more photo's like that?

Harrymann I did hear that the ogival shape improved low speed performanc; anyway inersting stuff

my belief however is that is was not planned I'll bet they got a serrendipitouslu good planform and then wrote equations for it afterwards---it's a shame we're not looking ahead into the hypersonic region too much wrt passenger aircraft,...the new stuff being submitted looks too unreliable to ever get through FAR 25

PA

[HarryMann]

This would be low speed subsonic stuff, so take a guess, Re could be anything typical of fullsize flight, since model could be in a pressurised tunnel. Alpha. It may be alpha typical of rotation or flare, doesn't look too drastic though

Yes the variation on straight swept l.e. was for subsonic improvements, principally approach and landing speeds

[FullOppositeRudder]

Gliders and ballast

I would agree with your comments providing you prefaced them with "in still air".

Competition glider pilots stuff in loads of ballast when flying into a head wind to up their glide speed and increase their range (think headwind case equal to normal light weight glide speed when you would have zero range)

Mostly so, but it goes a little further. Here is a more detailed explanation of why we often use water ballast on days of strong lift:

Re: [GBSCstudents] Water ballast

As elsewhere in this discussion, it can get quite technical. Most weekend pilots go without the complications of ballast, and simply enjoy the pleasure of pure flight using solar power and genuine renewable energy - all free from the sun

[Flingwing47]

heavier gliders

Originally Posted by Joetom

Slow, clean and heavy. Make it easy I will try.

Wing needs to produce required lift, which it will do, I think Slow holds the simple key, wing moving slow allows more time for higher pressure air under the wing to find lower pressure air on top of the wing.

An easy to think of it could be, keep slowing the wing to zero speed and have magic higher pressure air under the wing, this hi pressure air would have all the time in the world to slip over the wing tip and find the low px air.

Well at least that's what I though I read many many years ago.

Anyone have an easy way to explaine why heavy aircraft glide further than lighter aircraft ? (engines switched off)

An aircraft glides the most distance at the best L/D ratio. For most aircraft that is at 4 degrees angle of attack. If you are heavier you have to go faster to create the greater lift.- but you are still using 4 degrees of alpha. So the glide angle and range are the same, just a faster speed.