Why don't they make airliners that fly higher?
Discussion
Okay, so we're not going to get another supersonic airliner any time soon, if ever. However, why don't they make planes that fly above levels at which turbulence can occur so, at least if we're going to be stuck up there for hours on end we can at least be guaranteed a perfectly smooth ride at cruising altitude? Is it that the awkward 'q corner' issue is always going to be the undoing of any attempt to make airliners fly high enough to guarantee smooth flight, or is there another reason why airliners have never evolved beyond flying at about 38,000* ft?
* Yes, I know they sometimes go a bit higher. We once touched 41,000 on a flight to BOS that was avoiding a big storm shortly before reaching St Johns, but generally 38,000 seems to be the usual limit.
* Yes, I know they sometimes go a bit higher. We once touched 41,000 on a flight to BOS that was avoiding a big storm shortly before reaching St Johns, but generally 38,000 seems to be the usual limit.
I think it's because oxygen levels would be too low for the engines to run efficiently, and the difference in air pressure between the outside of the plane and the inside would fatuige the airframe too quickly. Too make airframes cope with the difference would mean the planes would be heavier, and more expensive to build and buy.
Essentially, for the same reasons we won't be getting a supersonic airliner soon; wing design.
We are flying at altitudes which put our cruise speed not far above our low speed stall point, and just prior to the Mach buffet.
Any higher, and sonic wave drag would erupt.
That said, some aircraft are characteristically happy at different altitude/speed combinations. The 777 likes to hang low on an economy cruise, whereas Brand A aircraft tend to be happy up above.
Also, airlines aim to send their aircraft on routes which take advantage of the jet streams, which can give us over 150mph of tailwind help. Unfortunately, the edges of these jet streams are where the clear air turbulence exists, and it's very difficult to detect and forecast.
We are flying at altitudes which put our cruise speed not far above our low speed stall point, and just prior to the Mach buffet.
Any higher, and sonic wave drag would erupt.
That said, some aircraft are characteristically happy at different altitude/speed combinations. The 777 likes to hang low on an economy cruise, whereas Brand A aircraft tend to be happy up above.
Also, airlines aim to send their aircraft on routes which take advantage of the jet streams, which can give us over 150mph of tailwind help. Unfortunately, the edges of these jet streams are where the clear air turbulence exists, and it's very difficult to detect and forecast.
Dr Jekyll said:
Eric Mc said:
Vry few military jets these days use pure turbojets. They also use turbofans - but they are usually low bypass turbofans - and sometimes fitted with reheat as well.
How high do modern military jets go? I had an idea it's not as high as Canberras used to.Dr Jekyll said:
Eric Mc said:
Vry few military jets these days use pure turbojets. They also use turbofans - but they are usually low bypass turbofans - and sometimes fitted with reheat as well.
How high do modern military jets go? I had an idea it's not as high as Canberras used to.All military aircraft are specialised to some extent. The Tornado was originally designed primarilly as a low level bomber - so when they developed the interceptor version (the IDS/F3 family) it had some shortcomings.
In the late 1940s/early 1950s, the assumption was that high altitude was what would keep a bomber safely above anti-aircraft guns - so designs like the Canberra, Vulcan, Victor etc were designed to be able to cruise at over 50,000 feet.
In the early 1960s, it was realised that altitude no longer guaranteed safety and that low level was a better bet for survival, so bombers designed from that period onward were optimised for low level ground hugging, their preferred operational environment.
With the advent of stealth technolgy, high altitude came back into fashion to some extent.
In the late 1940s/early 1950s, the assumption was that high altitude was what would keep a bomber safely above anti-aircraft guns - so designs like the Canberra, Vulcan, Victor etc were designed to be able to cruise at over 50,000 feet.
In the early 1960s, it was realised that altitude no longer guaranteed safety and that low level was a better bet for survival, so bombers designed from that period onward were optimised for low level ground hugging, their preferred operational environment.
With the advent of stealth technolgy, high altitude came back into fashion to some extent.
Eric Mc said:
Concorde flew at 50,000 feet and the passengers didn't need spacesuits.
Concorde flew at up to 60,000 feet. However, it had to fly at Mach 2 in order to do so, and in the process burnt huge amounts of fuel and costing a fortune to the point of it becoming too un-economic to maintain!As long as passengers insist on paying £28 return to Malaga, there will be no huge step forwards other than making aircraft cheaper to operate!
Plus, air-crew can't operate day in - day out at massive altitiudes due to increase in exposure to radiation! It's debateable if working at 36,000 feet every day is even safe?! I think the concorde crews only operated 2 flights per week, thats hardly economic for an airline!
Sifly said:
Eric Mc said:
Not debating any of that.
But it is technically possible to fly any height you like without the need to wear spacesuits.
Not if you are planning on returning....................................alive!But it is technically possible to fly any height you like without the need to wear spacesuits.
a spacesuit just provides a pressurised environment that we can live in.
an aircraft cabin provides a pressurised environment that we can live in.
what's the difference in your opinion?
Sifly said:
Concorde flew at up to 60,000 feet. However, it had to fly at Mach 2 in order to do so, and in the process burnt huge amounts of fuel and costing a fortune to the point of it becoming too un-economic to maintain!
I thought it was the other way round, namely the higher the fly you faster you can go as there's less air resistance (until you run out of lift and mush out).Gassing Station | Boats, Planes & Trains | Top of Page | What's New | My Stuff