Good work ! Still two remarks : 1/- Have you thought of the *gull wing* solution for a low wing project ? Seems to work on a 380... and will improve the design (aerodynamics ) wing-to-fuselage connection ( perpendicular attachment )while shortening the landing gear legs. 2/- I notice that your props turn the same way...with 11,000 hp behind them, you have a massive torque effect while manoeuvering (right turn on a pitch-up, left on a pitch-down)...That will lead to piloting difficulties -and certification requirements on a *critical engine* (pitch-down moment on a right engine failure) or a serious study of autopilot controlled engine failure. IMHO, you'll have two solutions : 2-a/- Contra-rotating props (that will also improve your trans-sonic aerodynamics on the prop tips) 2-b/- opposite rotation directions on the props...which means an increased investment on spare parts...not my favourite idea.
Sounds exciting. I read in ATI that they were looking at a mid 80s size, but not the 70s...I hope it isn't a deplug of the 90 version. Deplugs are heavy and not really worth it. (look at the A318 vs the A320).
Cool that ATR caught on to a single baggage bay, I thought the 3 different points was a pain..and the largest compartment being in a shared area with pax boarding and galley service was stupid. And speed looks good, but is it enough?? Donno. We regularly push the Q4s right to the 360s...it is incredible when we get to Ottawa, some AC Airbus drivers complain how we leave them in the dust...beating them to YOW by 5 mins easy! ATR should go big...
That's what I kinda like about this Turboliner..big, fast. (Hey, maybe this is ATRs way of gauging public reaction to the next ATR, we could be influencing history here!)
Thnx for the responses. I was on a trip this week. In the week-end I will find time for a better look & maybe do a mark IV based on your comments.
Question 1: I included DLC to improve approach handling. Now it's spoilers + DLC spoilers, which seems overdone. Maybe they could be combined, any suggestions? Could save some weight / complexity.
Question 2: I included "active cooled power brakes" because thrust reverse works very well for props but makes a lot of noise too. No thrust reverse after landing & electric drive to the gate would really make a difference in total noise pollution. Is there a smart way to use the electric engines as generators during roll out & use the energy to cool the brakes? Or would it be simpler to put on the APU before landing to provide power to a blower/compressor?
On the low wings+ big props: I took a look & will post some configs I looked at. Think about the recent LH A320 wingtip incident.. http://www.youtube.com/watch?v=z42fchrzhHY Ground clearance would be a design concern.
On speed : Mach 0.7 is a lot of speed at 25k ft, the Turboliner should be able to do 440 knots like the bulkier A400M (max cruise M.72).
On prop tip fuselage clearance : I looked at A400M prop-fuselage clearance and added ~20%. Powerplants to far from the cg creates asymetric / 1 engine out issues (bigger tail, weight /drag)
Counter rotating props are being looked at by the OEMS indeed. They offer advantages (reduced rotor diameter) but also have some issues of there own I think: heavy gearboxes and noise (interference between props) e.g. I guess I sticked on the safe side with an existing engine / prop combination.
Opposite rotation seems possible (A400M has it too). Less trimming means less drag. It had so in post 1..
rgds
Last edited by keesje; 21st Apr 2008 at 08:28.
Reason: spelling
Delightful to see the original and lateral thinking. Kees, congratulations for pushing it beyond the first negative responses of the “it’ll never work” variety.
Maybe it won’t. But the thinking behind it – and the general response on PPRuNe – is surely being quietly observed by many an aeronautical enginner and market analyst in Boeing, Airbus and a few others.
Kiwilad in post 34 pointed out that most people don’t know/aren’t given a choice as to the aircraft type they’ll be traveling on. I agree, and I think an increasing proportion of travelers are more concerned with the combination of price/comfort/direct flight, not necessarily in that order. The relative speed advantage of a jet over a turboprop over 1-1.5 hour sectors, when considered in the context of all the time getting to an airport, checking in and waiting, just seems risible. And if you can get a TP aircraft closer to the passenger than would be possible with a jet, hurrah. Operators,as we’ve seen in the USA in the last few weeks, are more than a little concerned with the cost of fuel, however much they might have hedged.
In my industry, the rising fuel cost component is already nudging shipowners to reduce speed and maintain their weekly port call schedules by inserting another vessel in the cycle. It could be the seventh, the ninth or the eleventh ship but the savings are in the high millions. Sounds easy enough in liner shipping, yes, where there is an icreasing capacity glut; I know it’s more difficult in aviation where the parameters of fuel efficiency are much more restrictive. Just perhaps, you’ve come up with the right idea at the right time.
All you need now is a better name than "TurboLiner" and that reflects all the thoughtful PPRuNe input. That might perhaps better be left to JetBlast.
In the name of pax safety, place the seats facing rearwards. Make row 1 at the rear of the aircraft. If pax board via two doors, they will hardly notice the difference. Tilt the fixed seat-back angle at about 20 degrees and Take off angles will not be a problem. It might well be that seat fixings and rails can be of lighter construction and still maintain crash G criteria. Place the windows slightly lower in the fuselage to give the aisle seat pax a view outside. Who wants to look sideways anyway?
As I understand it, rear facing seats do have the advantage of being safer than forward facing seats for the pax in the event of an incident. Given proper structural design of course.
I believe the issue with them, or all airliners would have them already, is that the loads are placed higher into the back of the seat, therefore requiring a stiffer structure to resist the forces in the event of a sudden deceleration. {Forward facing seats put the loads into the seat at seatbelt level.} Which therefore requires a stronger floor, therefore a bit more weight, therefore increased cost of fuel per flight, therefore increasing the operational costs of the aircraft ...
I'm not sure how much of an impact this would have in terms of a relatively short haul aircraft like the Turboliner, but it would be a consideration. Economics vs. innovation as always.
Keesje - interesting design. Hopefully I'll get a chance to fly in it or something like it someday.
Thnx for your kind words. As you mention challenges in shipping, automotive and aerospace aren't that different if you look at them from a distance. All are balanced trade-offs that move when the environment changes. Old, shelved ideas become feasible again.. Everybody check their archives !
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All you need now is a better name than "TurboLiner" and that reflects all the thoughtful PPRuNe input. That might perhaps better be left to JetBlast.
Be my guest , the combined creativity of PPRuNe should be able to come up with something better!
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In the name of pax safety, place the seats facing rearwards.
rubik101. Interesting idea. I think the Aerospace community concluded rearward facing seats are a good idea decades ago. It's up to the airlines, as you say little technical complications. Still no one uses them. I'm thinking about doing the rows in front of the emergency exit rearward, leaving a choice to the passengers. Maybe statisticly the seats after and in front of the wing would offer similar safety (an aircraft seldom crashes on its tail..)
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Place the windows slightly lower in the fuselage to give the aisle seat pax a view outside. Who wants to look sideways anyway?
Yes, the size / location of the windows always is a compromise. Weight, light, the bright sun beam above the clouds, the view from the middle / aisle seats.. Big windows seem fashionable now, composites allow for it I guess.
787
IMO the rooftop windows could improve the experience in the cabin, specailly for aisle passengers. It a dense cabin, being able to see the blue sky / sunlight entering the cabin could improve the general admosphere.
Talking about the windows, nobody questioned the higher windows next to the doors. They have a double function : allowing the crew to easily see what's outside before opening the doors & provide natural light in the galleys / lavatory areas. For an aircraft doing up to 8 flights a day this could prevent docking damage / enhance working conditions during intense crew / catering work.
I thought the above version would be the final one, but I guess another one. Any additional modifications / insights /ideas?
Skip the thought on low windows... I'm over 6 feet tall and have to slouch to see anything. Sure, bring the lower part of the sill down, but the topp sill should be created to maximise viewing angle for someone of my height (it IS all about me). Mind you, where I usually sit on a plane, I have the best veiw of all!
I think Broadreach hit it on the head...there's got to be a trawler or 2 here from OEMs...what do you plan on doing with yout idea when you're done? Sell it? Just hope an oem picks it up for bragging rights?
Hell, DO you work for an OEM and you're getting a feeling for what we pilots want? That's cool by me too! You don't have to say who ya work for, I'd just be damn glad someone asked a pilot's opinion before they build the thing!
Hello, Keesje. Quote :"...thrust reverse works very well for props but makes a lot of noise too. No thrust reverse after landing & electric drive to the gate would really make a difference in total noise pollution. Is there a smart way to use the electric engines as generators during roll out & use the energy to cool the brakes? Or would it be simpler to put on the APU before landing to provide power to a blower/compressor? " 1/- You can do away with reversers altogether, the props give enough drag in the Betra range ( you'll need to keep that one, if only for line-up ! ) and a 1500 m runway should be ample for your performance. 2/- I do not think that the brake cooling is that much of an issue : your landing speeds would be a lot lower than on an equivalent jet and it's not as though the brake temps would shoot-up immediately. 3/- Why not go a bit further and have an APU auto-start + auto switching to the APU generator after landing. As you'll need some cooling / temp stabilisation time before you cut the engines off, the transition from traction to wheel drive would be very smooth.
Now a few issues with the flight controls : at the speeds you're considering, a trimmable horizontal tail is the best choice --> The to-day position needs to be re-designed again. The high-lift devices solution are still not very clear...and the roll control ? high speed aileron, spoilers, low speed ailerons/flapperons ?
The principle of regenerative braking is already very well established in the automotive and railway worlds...so your wheel-motors would ,presumably be fixed stators with rotating discs (hall-effect)...the disc could also be used as a brake-disc.
regarding the main engines, I understood they needed to run a while for temperatures to stabilise. Unlike a car, you couldn't just drive your overgrown electric golf-buggy to the end of the runway, switch from "drive" to "ignition ", light the fires and "balls to the wall"
so, you'd still need the engines startedwell in advance of takeoff.
would the fuel-burn be considerably less than running the APU?
what would be the feasibility of a big generator built-into the main engine(s) to power the gear-propulsion ? this could "drop-out" at a pre-determined engine RPM, saving mechanical drag.
(or is the on-board battery-system envisaged to store sufficient power for ground-manoeuvers?
I would make sure it is possible to close the window blinds on the roof windows while standing in the aisle , blazing midday sun on your face when you trying to doze could result in air rage!
We have got to come up with some new ideas or we will not have an industry to work in. Have you thought of talking to the Royal Aeronautical Society - you might get some worthwhile feedback from some of the people there.
"New Truths are first ridiculed, then violently opposed, and then accepted."
In the name of pax safety, place the seats facing rearwards.
Rubik101, as firelight said, seats would become heavier. Current seats are designed for 16g forward. Backward facing people could survive (much) more. However the rest of the aircraft structure not. So I guess at 30g you and the seat could maybe survive but the rest of the aircraft would crunch. Thinking about it, I can not remember a 16 g kind of crash. It always seems less or so much more nothing helps..
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1/- You can do away with reversers altogether, the props give enough drag in the Betra range ( you'll need to keep that one, if only for line-up ! ) and a 1500 m runway should be ample for your performance. 2/- I do not think that the brake cooling is that much of an issue : your landing speeds would be a lot lower than on an equivalent jet and it's not as though the brake temps would shoot-up immediately.
Lemurian, I have the feeling thrust reverse should remain an option. The props have the mechanism anyways. On slippery runways, tail wind etc. they could be a usefull fall back option. Your second suggestion is very valid I realize. If this is to be a 737/A320 replacement dedicated for short high frequency flight, as I stated in the opening post, very short airfield performance is not a basic requirement. It could be an optional package. I left the power brakes out of the later concepts.
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3/- Why not go a bit further and have an APU auto-start + auto switching to the APU generator after landing. As you'll need some cooling / temp stabilisation time before you cut the engines off, the transition from traction to wheel drive would be very smooth.
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regarding the main engines, I understood they needed to run a while for temperatures to stabilise. Unlike a car, you couldn't just drive your overgrown electric golf-buggy to the end of the runway, switch from "drive" to "ignition ", light the fires and "balls to the wall"
Cockney Steve, Lemurain, I guess the engines should be started on a specified time and place. I guess it would depend on the airport layout / time/ distance to the runway. LCY and AMS northern "polderbaan" are two extremes. I think a system that can be (de)activated by the crew and performs all actions in sequence monitoring engine parameters, outside conditions etc. would be a doable / practicle solution.
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Now a few issues with the flight controls : at the speeds you're considering, a trimmable horizontal tail is the best choice --> The to-day position needs to be re-designed again. The high-lift devices solution are still not very clear...and the roll control ? high speed aileron, spoilers, low speed ailerons/flapperons ?
The horizontal tail has the similar configuration as the ARJ family. Maybe something better is possible. I made a conservative choice. The highlift devices are a single slotted flap and a flaperon similar to e.g. the 777. http://youtube.com/watch?v=jOG4A1_99mo (I included it in the picture)
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would the fuel-burn be considerably less than running the APU? what would be the feasibility of a big generator built-into the main engine(s) to power the gear-propulsion ? this could "drop-out" at a pre-determined engine RPM, saving mechanical drag. (or is the on-board battery-system envisaged to store sufficient power for ground-manoeuvers?
The Wheeltug guys claim a lot of fuel can be saved, easiliy compensating the weight of the electromechanical components. I think batteries to supply the amounts of energy required would get very heavy. Batteries get better and better, but very slowly..
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I would make sure it is possible to close the window blinds on the roof windows while standing in the aisle , blazing midday sun on your face when you trying to doze could result in air rage!
Capster, you are right I foresee the window would be semi transparent, spreading the light into the cabin. Passengers can see the sky is blue but not much more. Of course crew should be able to dim it or shut it like other cabin windows.
Keesje, Fantastic concept my friend. I can appriciate what your trying to do, blend the advantages of jets and TP's.
The 6 abreast seating is a great idea for a start. I fly the 146, and as far as I can tell, most pax prefer a roomy, quiet cabin, rather than the engine type (jet or prop) It's irrelevant if you can keep the noise down inside your cabin, noise and vibration are the key factors in pax comfort.
Regarding your idea of taxiing out with your engines shut down, using the electric drives, I'm certain at LCY (where I fly the 146 into ) this wouldn't be advantageous. Holding times at WORST in my experience are 10-15 mins. And backtracking down the runway requires a higher than normal taxi speed. I'm not sure your electric drives could produce up to 30knots in taxi speed. And to be honest, using TP engines, your fuel efficiency is higher than a regional jet anyway, so I would guess that any fuel saving from taxiing with your engines shutdown will be negligible.
Another thing about starting your engines at the runway (or near it) that concerns me is electrical power. Considering your APU will be running your electrical drives, as well as the entire AC system of your aircraft, The chance for failure of the APU generator is higher. Imagine if your APU/APU generator failed on taxi out. Your aircraft would come to a halt in the middle of the taxiway. With no AC electrical power. PA system wouldn't work so communications with cabin crew and pax would be difficult, and if at night, cabin plunged into darkness with only emergency lighting. Not good.
Also the late starting of engines poses problems (again)
Say one of your engines won't start or you suffer a hot start or even a fire. You have no ground crew support. Evacuation of pax (if required) would be a major problem, considering you may have other aircraft infront and behind you. And the clousure of a whole taxiway (or even the airport) is a possibilty, what with a fire damaged A/C and 160+ pax on the loose near an active runway.
I'd say ditch these drives (it's just something else that needs to be maintained) And your onto a winner.
As for your window at the door being elevated up, it's a nice idea, but can't you just build it into the door? The door is a heavy system anyway...
Also while I remember, If one of your wheel drives fails, that could be an embaressing moment for the crew.
Par exemple,
Both crew being 'heads in', say dealing with a problem. (naughty, I know, but not unfeasable is it?) One of your drives fails, and asymetrically, the aeroplane rolls onto the grass. (or water at LCY ) Or say one of the drives jams up, It could be akin to using full braking on one wheel. ATC frown upon aircraft doing handbrake turns, it's considered a tad rude.
Also could you dispatch with one inop? Airliners have built in redundency in most systems to allow dispatch with a number of components inop. Would just one of your wheel tug thingies have enough power to move the aeroplane?
If certification deems it necessary that both be working, it wouldn't be fun to ground an aeroplane for something that doesnt even affect it when it's flying!
And even if you could 'switch off' the working one and taxi out on engine power, your defeating the purpose of having them installed. I imagine alot of airlines would eventually remove them anyway. Less cost, weight (and as you've stated; less weight=more pax) and complexity
Just like re-enforced flight deck doors and CVRs for example, manufacturers will only install things when they have to by law. And why? Because the airlines want a machine that is as simple as legally possible.
(granted these are safety related items, but you see my point?)
I know I've banged on about these drives but they just stick out to me as a bit unnecessary.
Just a thought
(I always think of failures, too much RJ/146 flying!!! )
Keesje, my comment re the name was really tongue-in-cheek. That sort of thing is usually done by testing random groups of travelers anyway, not by asking a hoary sampling of ppruners.
In your #58 you said
Quote If this is to be a 737/A320 replacement dedicated for short high frequency flight, as I stated in the opening post, very short airfield performance is not a basic requirement. It could be an optional package. Unquote
I wonder. My earlier comment about getting the airplane closer to the passenger really meant getting it into smaller regional airports provided the demographics are right. That seemed sensible to me partly from of the fuel consumption aspect: small airports where turnoff to gate is two-three minutes vs big ones where it could be ten, fifteen, plus holding for other traffic to pass. I realise that would require big rethinking of ATC, terminal facilities, who pays for the new navaids etc but with fuel going the way it is, those little things seem likely to make a big difference in overall operating costs.
I'm probably with Atreyu re electric drives if only based on there being one more thing to go tech.
And I’m totally with mcnuggit re the windows. Hell on the spine having to scrunch down to see outside. Yes you can hear me muttering “Viscount, Electra….”
Atreyu, broadreach, thnx for your ideas. Regarding the failure rate of the electric drive system, I guess a suitable MTBF could be engineered in. If it is not functioning a (slow) push back on one drive should be possible, or a conventional tug could do the job. It's not a no go item.
Still if it works 99.x % of the time it means a dramatic reduction of airport noise & air contamination. It might pursuade airport authorities to allow more flights or at early/late hours or alternative runways. For e.g charter and low cost airlines this would add value compared to existing types.
Of course a lighter simplified ATR / BAE 146 type of gear could be specified. I included it in the sketch.
Changes compared to earlier sketch:
Additional escape window (required)
Alternative simplified main landing gear
Wing - engine pylon fairing
Belly access doors
It would be nice to have feedback from folks from fleet management departments / OEMS. What would be the best way to get their opinions?
I am sure that this is not the sort of feedback that you are looking for but it may nevertheless be useful. Speaking as a passenger, I used to commute regularly between Lagos/Ibadan/Kaduna/Benin, over a period of 4 years, some time ago.
The workhorse of these routes was the F27 but occasionally an F28 was used.
There was a huge difference in ‘comfort’ between these two. The noise/vibration/harshness of the F27 was not something that one looked forward to. But more importantly, IMO, it was the limited service ceiling or cruising ceiling that made the F27 particularly uncomfortable because most of the time it could not rise above the bumpy air. The type of discomfort I am talking about is not just a regular jolt or two that people nowadays seem to refer to as turbulence. No, this was the real difficult stuff that could pin the cabin staff to the ceiling for a good few seconds, and leave one's hips bruised and chaffed by the seatbelt. I therefore developed an aversion to the F27 and their ilk. In the F28, I could often see the weather well below, and could walk straight when I got off.
Would your design be better than this for comfort? If not, passengers will eventually shun it. The answer is to design one that can get above the weather, easily. Is a 25,000ft service ceiling enough? Wasn't that the service ceiling of the Bristol Britannia in the 1950s? Surely engine and propeller technology has improved since then.
I follow your posts with interest, on Airlinersnet as well, if I am allowed to say that.
rgds
All you need now is a better name than "TurboLiner" and that reflects all the thoughtful PPRuNe input. That might perhaps better be left to JetBlast.
, the combined creativity of PPRuNe should be able to come up with something better!
. I think the Aerospace community concluded rearward facing seats are a good idea decades ago. It's up to the airlines, as you say little technical complications. Still no one uses them. I'm thinking about doing the rows in front of the emergency exit rearward, leaving a choice to the passengers. Maybe statisticly the seats after and in front of the wing would offer similar safety (an aircraft seldom crashes on its tail..) 
any inspiration? 
) this wouldn't be advantageous. Holding times at WORST in my experience are 10-15 mins. And backtracking down the runway requires a higher than normal taxi speed. I'm not sure your electric drives could produce up to 30knots in taxi speed. And to be honest, using TP engines, your fuel efficiency is higher than a regional jet anyway, so I would guess that any fuel saving from taxiing with your engines shutdown will be negligible.
) Or say one of the drives jams up, It could be akin to using full braking on one wheel. ATC frown upon aircraft doing handbrake turns, it's considered a tad rude. 
