Schorsch has explained it but Paul if you visualise a right angled triangle as pictured below, then look at the formula of

Vimd or minimum drag speed (which is the speed we have to fly at for best glide ratio) will be higher by a factor proportional to the square root of the weight increase.

This formula is basically saying that if we increase our weight then to obtain the best glide ratio or Vimd (minimum drag speed), we have to increase our speed by a factor proportional to the weight increase. Remember regardless of what our Vimd speed is we will still travel the same distance specified on that triangle provided we glide at that new Vimd speed, so the glide angle as shown on the triangle stays the same, as does the distance, we will just travel along the path of the glide path line on the triangle faster, meaning we will have a higher rate of descent.

Does this make it any clearer? (cos I’m confusing myself now LOL)

Dean

The Air Transat 330 glided 85 miles from 13,000 feet.
http://aviation-safety.net/database/record.php?id=20010824-1

Newforest

Mate the Air Transat glided 21,500ft in 77nm (or 88.5 statute miles) to end up at 13,000ft 8nm from the runway threshold. This is a glide ratio of about 1:21 which is excellent.

Dean

A 744 as with any plane could potentially stay in the air on one engine, but if you take a 747 for example that is cruising at FL350 and it lost 3 engines, the issue here is whether this engine will be able to create enough thrust to remain in the air at that altitude, (the engine is set to max continuous power), the answer is no it can’t (normally), so there is a thing called a driftdown procedure that is used whereby it can (not that it has a choice) descend to an altitude whereby the air is dense enough to produce the required thrust.
This means that, as the aircraft descends, the thrust increases and the driftdown angle becomes progressively shallower until it reaches zero and the aircraft stabilises. The driftdown angle becomes steeper at heavier weights and the heavier the a/c is the lower the stabilising altitude.

The driftdown is flown at the best angle of climb speed, VX, which is VIMD (minimum drag speed) for a jet and is also the best (least) angle of descent speed.

This procedure is particulary problematic if the driftdown altitude is lower than say The Alps etc.

Hope this helps

Dean

I bought it on ebay a few months ago for £28 (delux edition) twas brand new, well worth the money

Any of the Bristol lads (and others) up for a Bristol – Innsbruck day trip? 😉

Great pics Adam, I particularly like the Thomas Cook Airbus 330, also the way you have captured the Saudi 777 makes her look like a gracious swan coming in for a landing on the water, very nice.