Why design a passenger aircraft with a high wing?
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Capot, I think that you have the main points,
One more is less ingestion upon applying reverse thrust? Like less prop damage, I remember the E110 props taking a punishing on unprepared strips.
The ATR looks like a good design.
One more is less ingestion upon applying reverse thrust? Like less prop damage, I remember the E110 props taking a punishing on unprepared strips.
The ATR looks like a good design.
I'm glad John Farley's potential redeployment to Hatfield never happened, as he'd never have been able to demonstrate a 146 as impressively as a Harrier!
Apart from that, without looking it up I'd have put the 146 as slightly later than 1966 and I think we were only up to 144 by then. But as he says, and as I implied, it was designed as a third-world feeder liner with similar short and rough strip capability to the Avro 748 and that had been the design aim from the beginning. Another design aim was quietness, and Orange County was a good example of the extra destinations that become available as a result. London City's another (and it's also pretty short).
The 146 was launched by Hawker Siddeley, but put to one side as a consequence of the 1973 oil crisis and the inflation that ensued. By the time things cleared up sufficiently for a re-launch, we were nationalised as British Aerospace.
As for three-engined ferrying, during the early development flying starter quill-shaft breakage was rather common and I recall one flight which therefore took off on three but flew and landed on four after a windmill in-flight start!
Apart from that, without looking it up I'd have put the 146 as slightly later than 1966 and I think we were only up to 144 by then. But as he says, and as I implied, it was designed as a third-world feeder liner with similar short and rough strip capability to the Avro 748 and that had been the design aim from the beginning. Another design aim was quietness, and Orange County was a good example of the extra destinations that become available as a result. London City's another (and it's also pretty short).
The 146 was launched by Hawker Siddeley, but put to one side as a consequence of the 1973 oil crisis and the inflation that ensued. By the time things cleared up sufficiently for a re-launch, we were nationalised as British Aerospace.
As for three-engined ferrying, during the early development flying starter quill-shaft breakage was rather common and I recall one flight which therefore took off on three but flew and landed on four after a windmill in-flight start!
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Can't think of many modern prop driven aircraft with a low wing other than the ATP
High wing advantages :
No worry about prop clearance so props can be large/not close to the ground for rough field/gravel operations (what sold many of the F27s compared to the 748 in the 1960s-70s).
No wing spar through the cabin which you still get on smaller low-wing types like the Jetstream.
Same is true for jets, especially the clearance. Note the smaller types are either high wing (146 and Do328 jet), have to be rear engined (RJs and business jets) or have bizarre inefficient configurations (VFW614 with engines on top of the wing).
No worry about prop clearance so props can be large/not close to the ground for rough field/gravel operations (what sold many of the F27s compared to the 748 in the 1960s-70s).
No wing spar through the cabin which you still get on smaller low-wing types like the Jetstream.
Same is true for jets, especially the clearance. Note the smaller types are either high wing (146 and Do328 jet), have to be rear engined (RJs and business jets) or have bizarre inefficient configurations (VFW614 with engines on top of the wing).
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I remember the PSA pilots referring to them as "four oil leaks connected by an electrical fault." The Lycs were indeed a disaster (at least the early aircraft); the company I worked for had three aircraft and in the space of a year we had 12 engine changes, about half of them inflight failures.
Last edited by org; 27th Aug 2008 at 13:14. Reason: typo
I remember the PSA pilots referring to them as "four oil leaks connected by an electrical fault." The Lycs were indeed a disaster (at least the early aircraft); the company I worked for had three aircraft and in the space of a year we had 12 engine changes, about half of them inflight failures.
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First time poster & boffin not pilot, so be gentle
Long-ish post too
I'm a systems guy nowadays but was once educated in the dark arts of the 'future concepts' bit where you come up with an aircraft configuration.
There's really only two good reasons to build a high wing aircraft, and they're not mutually exclusive
1) Cargo handling/ground access to the fuselage
2) to put the engine intakes clearly out of the way of FOD (note intakes, not props)
Cargo handling covers both putting the floor near the ground handlers and making a nice big rectangular box. Most high-wingers have the wing cutting through the fuselage where it's otherwise too narrow to be of use to the cargo area.
So for pax aircraft, you do it because you anticipate operating places that don't have airstairs or other heavy support equipment. The SLF can get on & off using only what the aircraft brought with it. There is a side advantage here that the turn-around time is reduced, since you don't have to wait for any outside kit to move about - so you save a time on each turn around. I'd guess that's why the ATR & Dornier x28s are high up - I'm not aware of them being rough field capable but haven't played with them.
(Aside - that's why most biz jets are rear-engined, because otherwise the ground clearance would be so high, kit would be needed to get the Pax off - but the drag penalty of a high wing is too much)
And FOD - on a high wing, the fuselage can be relied on to block all of the nosewheel debris & spray. With a low wing (wing-mounted or rear engines), you have to assume likely spray & debris weights - and paths - only as far as the regulations say you do. A high mounted engine means that's not an issue. You've only got to worry about the engine sucking stuff up directly.
There's only a small lift benefit from the high wing, a big drag penalty - doubly so at >Mach 0.7-ish & it will always weigh more than mid/low wing, so you need a distinct operational reason to want to pay that. With the same engines, you can almost always make the low wing have better field performance for a given range-payload than a high wing due to structural weight.
Any stability benefits are secondary - you don't configure the airplane to make the flight control guys job any easier.
Long-ish post tooI'm a systems guy nowadays but was once educated in the dark arts of the 'future concepts' bit where you come up with an aircraft configuration.
There's really only two good reasons to build a high wing aircraft, and they're not mutually exclusive
1) Cargo handling/ground access to the fuselage
2) to put the engine intakes clearly out of the way of FOD (note intakes, not props)
Cargo handling covers both putting the floor near the ground handlers and making a nice big rectangular box. Most high-wingers have the wing cutting through the fuselage where it's otherwise too narrow to be of use to the cargo area.
So for pax aircraft, you do it because you anticipate operating places that don't have airstairs or other heavy support equipment. The SLF can get on & off using only what the aircraft brought with it. There is a side advantage here that the turn-around time is reduced, since you don't have to wait for any outside kit to move about - so you save a time on each turn around. I'd guess that's why the ATR & Dornier x28s are high up - I'm not aware of them being rough field capable but haven't played with them.
(Aside - that's why most biz jets are rear-engined, because otherwise the ground clearance would be so high, kit would be needed to get the Pax off - but the drag penalty of a high wing is too much)
And FOD - on a high wing, the fuselage can be relied on to block all of the nosewheel debris & spray. With a low wing (wing-mounted or rear engines), you have to assume likely spray & debris weights - and paths - only as far as the regulations say you do. A high mounted engine means that's not an issue. You've only got to worry about the engine sucking stuff up directly.
There's only a small lift benefit from the high wing, a big drag penalty - doubly so at >Mach 0.7-ish & it will always weigh more than mid/low wing, so you need a distinct operational reason to want to pay that. With the same engines, you can almost always make the low wing have better field performance for a given range-payload than a high wing due to structural weight.
Any stability benefits are secondary - you don't configure the airplane to make the flight control guys job any easier.
Do a Hover - it avoids G
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RugGun
I would be interested to know why you assert that a high wing layout will always be heavier than a low or medium one.
JF
I would be interested to know why you assert that a high wing layout will always be heavier than a low or medium one.
JF
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To some extent, it depends on the choice of engine mounting position. I think a rear engine mount is the heaviest at most Pax aircraft sizes (a la MD-80, not DC-10). This is size dependant - smaller you get, less the problem is.
The fuselage floor must, in some manner, be supported by the wing. In a low & mid wing, the job of the fuselage structure is basically not to collapse under bending & its own weight during manoeuvring and to cope with aero loads & pressure differences.
Structurally (big simplification coming) a low or mid wing airplane is two box sections assembled in a cross, bolted to each other, with a stiffened balloon or tent for the fuselage.
A high wing has the same two primary members, but also needs a support frame at least 5 feet high between them.
As a result, in a high wing, the fuselage bending is exactly the same as any other configuration with the same engine loc'n relative to the wing - so the skin thickness is at least the same as the low. But you also need to thicken the centre section to transmit floor loads up to the wing.
In the event that you fuselage mount the main gear, although you can save undercarriage length - and the associated weight too - you need an additional lump of structure approximately like the wing centre box sitting between the gear, which I think more than cancels it out. Or you need to further thicken the centre section skins.
You only do that if you want to absorb high sink rates (easier with legs that are shorter once loaded) and/or house the tyres in the belly because the engine nacelles are too small or unusable. The tyre size is only a feature of the desired bearing ratio/ground pressure.
I'm afraid I don't have the numbers to hand - I can dig something open source up over the weekend comparing high/low & underwing engine/tail mounted.
The fuselage floor must, in some manner, be supported by the wing. In a low & mid wing, the job of the fuselage structure is basically not to collapse under bending & its own weight during manoeuvring and to cope with aero loads & pressure differences.
Structurally (big simplification coming) a low or mid wing airplane is two box sections assembled in a cross, bolted to each other, with a stiffened balloon or tent for the fuselage.
A high wing has the same two primary members, but also needs a support frame at least 5 feet high between them.
As a result, in a high wing, the fuselage bending is exactly the same as any other configuration with the same engine loc'n relative to the wing - so the skin thickness is at least the same as the low. But you also need to thicken the centre section to transmit floor loads up to the wing.
In the event that you fuselage mount the main gear, although you can save undercarriage length - and the associated weight too - you need an additional lump of structure approximately like the wing centre box sitting between the gear, which I think more than cancels it out. Or you need to further thicken the centre section skins.
You only do that if you want to absorb high sink rates (easier with legs that are shorter once loaded) and/or house the tyres in the belly because the engine nacelles are too small or unusable. The tyre size is only a feature of the desired bearing ratio/ground pressure.
I'm afraid I don't have the numbers to hand - I can dig something open source up over the weekend comparing high/low & underwing engine/tail mounted.
Last edited by RugGun; 26th Sep 2008 at 14:21. Reason: grammar!
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Embraer are currently developing a freighter based on the very successful 190 series. It's almost the same aircraft but with the wing mounted high and a cargo ramp added. The reason given to me by my friends in San Jose dos Campos is get the engines away from the ground and the ramp close to the ground.
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That's the classic configuration for a purpose-built freighter. Ben Howard of DGA fame designed a small twin about 1939 with high wing, ramp-loading tail, called it DGA-10. Never built, unfortunately, but it had plenty of follow-ons by Curtiss, Budd, Fairchild, Lockheed, DHC & McD-D - plus the Argosy and Transall in Europe - and the Il-76 and Antonovs etc etc.
I was sent to Hatfield in 1981 to evaluate the 146, as a replacement for twin t/props, especially on hot 'n high operations with unsupported stops at very basic airfields. I don't think it had even flown by that time.
I remember a great deal being made of the fact the the aircraft could carry a complete spare engine, in a number of boxes, in the hold.
I mentioned that in my report as a huge advantage, to the amusement of the boss, an aircraft engineer by background.
"Why do you think they're promoting that?" he said, roaring with laughter, "it's because they're expecting lots of engine problems". He also suggested that I was a "gullible plonker", which was probably right.
I remember a great deal being made of the fact the the aircraft could carry a complete spare engine, in a number of boxes, in the hold.
I mentioned that in my report as a huge advantage, to the amusement of the boss, an aircraft engineer by background.
"Why do you think they're promoting that?" he said, roaring with laughter, "it's because they're expecting lots of engine problems". He also suggested that I was a "gullible plonker", which was probably right.
Joking aside, it was often a serious problem for the operator if an engine did go u/s at an outstation.
With the 146 it was sometimes possible to ferry back to somewhere sensible and do an engine change in comfort, but in general if you were stuck at a difficult airfield (and Sod's Law says you would be), only another 146 could bring spare engine modules in. However it could do that, which most of the opposition couldn't.
You didn't have that problem with mainliners connecting "proper" aerodromes.
With the 146 it was sometimes possible to ferry back to somewhere sensible and do an engine change in comfort, but in general if you were stuck at a difficult airfield (and Sod's Law says you would be), only another 146 could bring spare engine modules in. However it could do that, which most of the opposition couldn't.
You didn't have that problem with mainliners connecting "proper" aerodromes.
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The ATP was also knicknamed the "Sky Skoda". For me the early ATP DV window seal was a nice touch, a piece of sticky foam that looked like old fashioned draught excluder from B&Q.
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I believe the main two pillars of aircraft designing are
- Range and
- Capacity
Every decision is taken to satisfy these two criteria correlated to financing and practicality of physics.
When you say passenger aircraft, you need to specify if it is a short range small to medium capacity aircraft or a medium, extra range/long range aircraft.
For instance an aircraft that fly short range with medium capacity may not require to gain a faster speed and high service ceiling. Hence, a design with straight wings, turbo prop engines would be feasible. Generally, passenger aircraft such as F-27 is designed as hi-wing for certain reason.
- Since the range and capacity is short and small, no need of jet engines, but couple of turbo prop engines would do the job in a most economical way
- Using prop blades need some ground clearance
- Since, airplanes with short range and low capacity doesn’t require higher speed, their wing construction is less complicated (tapered rectangular wing) than of a high speed jet. So most of turbo props place the simple wing on top of the fuselage as it doesn’t require heavy “reinforced wing-carry box” , which is heavy and complicated.
- Hi-wing is aerodynamically has good characteristics at lower speeds-perfect for small/medium props. (pendulum effect)
On the other hand, fast jetliners have totally opposite characteristics. Most passenger jets such as Boeing 777 are having low wing configuration. Following are some of the reasons for selecting a low wing configuration for such aircraft.
- As their capacity is high and range is longer, they require to gain much more speed than others. Jet engines serves this purpose in the most economical way.
- Low wing with high swivel angles has good aerodynamic characteristics at higher speed.
- Since the wing is complicated* in a long range hi speed jet the construction require a heavy wing carry box, which is most unluckily to be place on top of the fuselage.
(* Flaps, slats, ground breaks, ailerons, outboard flaps, inboard flaps, outboard air breaks , in board air brakes, wash out airfoil construction, thinner airfoil with small LE radius, variable sweep angles, etc. These kind of complexity is not seen in prop/turbo prop aircraft)
To summarize all: every aircraft is designed initially looking at two main criteria which are “range” and “ capacity”. All other decisions are taken once these two are defined. so a short range less capacity aircraft may not require to fly fast and at high altitudes. Hence the hi wing arrangement has the best aerodynamic characteristics for such an aircraft. On the other hand a plane with long range with heavy capacity may require to fly fast, at high altitudes which can be complimented by having a low wing configuration.
(some of the fast military jets have hi-wing configuration.Military aircraft design is totally different to designing civil jets. Certain rules and criteria do not apply to military aircraft design. )
- Range and
- Capacity
Every decision is taken to satisfy these two criteria correlated to financing and practicality of physics.
When you say passenger aircraft, you need to specify if it is a short range small to medium capacity aircraft or a medium, extra range/long range aircraft.
For instance an aircraft that fly short range with medium capacity may not require to gain a faster speed and high service ceiling. Hence, a design with straight wings, turbo prop engines would be feasible. Generally, passenger aircraft such as F-27 is designed as hi-wing for certain reason.
- Since the range and capacity is short and small, no need of jet engines, but couple of turbo prop engines would do the job in a most economical way
- Using prop blades need some ground clearance
- Since, airplanes with short range and low capacity doesn’t require higher speed, their wing construction is less complicated (tapered rectangular wing) than of a high speed jet. So most of turbo props place the simple wing on top of the fuselage as it doesn’t require heavy “reinforced wing-carry box” , which is heavy and complicated.
- Hi-wing is aerodynamically has good characteristics at lower speeds-perfect for small/medium props. (pendulum effect)
On the other hand, fast jetliners have totally opposite characteristics. Most passenger jets such as Boeing 777 are having low wing configuration. Following are some of the reasons for selecting a low wing configuration for such aircraft.
- As their capacity is high and range is longer, they require to gain much more speed than others. Jet engines serves this purpose in the most economical way.
- Low wing with high swivel angles has good aerodynamic characteristics at higher speed.
- Since the wing is complicated* in a long range hi speed jet the construction require a heavy wing carry box, which is most unluckily to be place on top of the fuselage.
(* Flaps, slats, ground breaks, ailerons, outboard flaps, inboard flaps, outboard air breaks , in board air brakes, wash out airfoil construction, thinner airfoil with small LE radius, variable sweep angles, etc. These kind of complexity is not seen in prop/turbo prop aircraft)
To summarize all: every aircraft is designed initially looking at two main criteria which are “range” and “ capacity”. All other decisions are taken once these two are defined. so a short range less capacity aircraft may not require to fly fast and at high altitudes. Hence the hi wing arrangement has the best aerodynamic characteristics for such an aircraft. On the other hand a plane with long range with heavy capacity may require to fly fast, at high altitudes which can be complimented by having a low wing configuration.
(some of the fast military jets have hi-wing configuration.Military aircraft design is totally different to designing civil jets. Certain rules and criteria do not apply to military aircraft design. )
Gosh, a good old fashioned thread Necromancer!
When I used to teach this stuff, we were left to our own devices how (universities are great like that), I actually decided we had four pillars
- Role
- Operating environment
- Available technology
- The regulations
Range and capacity will sort of sit between role and environment. Your discussion about the alternate benefits/disbenefits of different engine types and wing configurations pretty much falls into "available technology".
I absolutely agree that swept wings give better transonic performance by modifying Mcrit, but disagree that a low wing improves high speed performance particularly. It's more I suspect a case of since the length of the fuselage necessitates a long undercarriage, a high wing would put the engines too far off the ground.
G
I believe the main two pillars of aircraft designing are
- Range and
- Capacity
Every decision is taken to satisfy these two criteria correlated to financing and practicality of physics.
- Range and
- Capacity
Every decision is taken to satisfy these two criteria correlated to financing and practicality of physics.
- Role
- Operating environment
- Available technology
- The regulations
Range and capacity will sort of sit between role and environment. Your discussion about the alternate benefits/disbenefits of different engine types and wing configurations pretty much falls into "available technology".
I absolutely agree that swept wings give better transonic performance by modifying Mcrit, but disagree that a low wing improves high speed performance particularly. It's more I suspect a case of since the length of the fuselage necessitates a long undercarriage, a high wing would put the engines too far off the ground.
G
And, on a lighter note....
In the smaller aircraft range - I much prefer the high wing concept.
It makes it ever so much easier to stand under - in the shade and / or out of the rain - on one of 'those' days.......
Cheers from 'Dunnunda'. Stinkin' Hot one day, rainin' the next.....
In the smaller aircraft range - I much prefer the high wing concept.
It makes it ever so much easier to stand under - in the shade and / or out of the rain - on one of 'those' days.......
Cheers from 'Dunnunda'. Stinkin' Hot one day, rainin' the next.....
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at G
The four facts you have mentioned, I am not saying incorrect. Of course Range and the Capacity are not the only to be considered. My point was at the outset the main two decisions are nothing but Range and Capacity. of course all other factors come afterwords. and also mind that I am talking about civil designs.
Low wing has few advantages over high wing at high speeds. forget about aerodynamics!, it will be practically impossible to put a swept back wing with all flaps/slats, air break, ground breaks, spoilers, etc on the top of the fuselage. If so, you will have to build a heavy wing box and make it structurally heavy: that will block the fuselage : reduce the effective capacity of the area.
Also another reason is to with stand the stress and force on the structure at higher speeds. In a low wing, having a wing carry box and putting the landing gear and fuel tanks make the wing box act like a center weight to the plane as well. Also the wing box can be made to with stand more stress than of putting in on top.
summarized: a transonic wing is most unlikely to be configured as a high wing but low wing configuration give more benefits. Hence most of the turbo jets/fans mission-ed to transport passengers medium to long range, place their transonic wing under the fuselage with a reinforced wing carry box.
(feel free to make a list of passenger aircraft with hi-wing with turbo jet/fan that fly at transonic speeds and same with low wing. you wont believe what you will find out.lol).
I agree for what you have said about "available technology" and of course we can't expect any extraterrestrial knowledge transform.
most importantly, don't take this personally. you may have spent all your life in teaching in the academic area or I respect you for whatever you have done. anyhow I wish if you could keep that dignity when you put your thoughts into words as well.
code0
The four facts you have mentioned, I am not saying incorrect. Of course Range and the Capacity are not the only to be considered. My point was at the outset the main two decisions are nothing but Range and Capacity. of course all other factors come afterwords. and also mind that I am talking about civil designs.
Low wing has few advantages over high wing at high speeds. forget about aerodynamics!, it will be practically impossible to put a swept back wing with all flaps/slats, air break, ground breaks, spoilers, etc on the top of the fuselage. If so, you will have to build a heavy wing box and make it structurally heavy: that will block the fuselage : reduce the effective capacity of the area.
Also another reason is to with stand the stress and force on the structure at higher speeds. In a low wing, having a wing carry box and putting the landing gear and fuel tanks make the wing box act like a center weight to the plane as well. Also the wing box can be made to with stand more stress than of putting in on top.
summarized: a transonic wing is most unlikely to be configured as a high wing but low wing configuration give more benefits. Hence most of the turbo jets/fans mission-ed to transport passengers medium to long range, place their transonic wing under the fuselage with a reinforced wing carry box.
(feel free to make a list of passenger aircraft with hi-wing with turbo jet/fan that fly at transonic speeds and same with low wing. you wont believe what you will find out.lol).
I agree for what you have said about "available technology" and of course we can't expect any extraterrestrial knowledge transform.
most importantly, don't take this personally. you may have spent all your life in teaching in the academic area or I respect you for whatever you have done. anyhow I wish if you could keep that dignity when you put your thoughts into words as well.
code0