New big prop, facing the A320 & 737: TurboLiner.

[keesje]

Both Airbus and Boeing are comfortably sitting on their narrowbody duopoly and enjoying a huge narrowbody backlog.

No wonder both say a 737 / A320 replacement is "unfeasible" & they suggest "end of next decade".

I don´t think so. Turboprops are 20% more fuel efficient then comparable turbofans and other technologies have evolved.

Both 737 and A320 and made to do flights up to 3000nm while most are under 1000nm in e.g. Europe.

Time to start up powerpoint & draw some lines.

http://i191.photobucket.com/albums/z160/keesje_pics/Turbolinercomponents.jpg?t=1206318554

As you can see I integrated electric Wheeltug like drives in the main landing gear. This will enable the aircraft to "pushback" and taxi to / from the runway on its own (APU) power. Saving fuel and noise.

http://i191.photobucket.com/albums/z160/keesje_pics/Turbolinerdimensions.jpg?t=1206318623

The fuselage is a few inch wider then a BAE146 but has a different shape. 6 abreast is acceptable because of short trips I think. It is optimized for about 150 seats.

http://i191.photobucket.com/albums/z160/keesje_pics/Turbolinercabinconfigurations.jpg?t=1206321141


I have some more graphics. What do you think of the concept?

[411A]

It'll never be accepted by the fare paying customer, aka, the passenger.
And further, having flown quite large piston and especially turbopropellor aircraft in the past, and further remembering the eleven (IIRC) pitch locks on each Electra AeroProducts propellor...big propellors present ever-bigger problems.

Bad idea, that is never likely to see the light of day.

[Dan Winterland]

It's got some merits, but there are lots of detractors as well.

It's a turboprop. Passengers don't like turboprops (as 411 has said) which is one reason why you see more regional jets around these days. Also, turboprops need a lot of maintenance. propellers are very costly to maintain and one of the main reasons a turboprop gets stuck on the ground with tech problems.

Turboprops fly slower than jets. It will get stuck at lower levels to keep it out of the way making it slower and more costly to run. the RAF found this with their new C130s. Although it had the ability to fly higher than the older C130s, it just isn't usually allowed to climb to jet levels.

At highest density seating, it's only really a competitor to the A319 and shorter B737s. This will limit the market.

Built in powerpushes have been looked at before. The weight penalty doesn't make them attractive. besides, if it's a turboprop - why not give it the ability to reverse using the engines?

Rooftop windows? Why? It's just another hole in the pressure hull and will add to the cost.

I would see it would have a future in developing markets with poor infrastructure - turboprops have better short field performance. But in Europe or the US, it's probably not going to make an impact.

[keesje]

Thnx for responding!


It'll never be accepted by the fare paying customer, aka, the passenger.
And further, having flown quite large piston and especially turbopropellor aircraft in the past, and further remembering the eleven (IIRC) pitch locks on each Electra AeroProducts propellor...big propellors present ever-bigger problems.

Bad idea, that is never likely to see the light of day.



Although the latest generation of turboprops has addressed some of the comfort issues by flying above turbulence and providing quieter cabins, analysts say the airlines' money worries about their bottom line now outweigh any passenger preferences.
With jet fuel prices 60 percent to 70 percent higher than a year ago, regional jets no longer offer good economics for short-haul flights, said Michael Dyment, an aviation analyst at Nexa Capital Partners, a Washington, D.C. (http://www.wtopnews.com/?nid=733&inform_keyword=Washington%2c+DC), corporate finance group.
"Nowadays, operating efficiency trumps any passenger considerations," Dyment said.
The world's remaining manufacturers of turboprops for commuter airlines, Canada (http://www.wtopnews.com/?nid=733&inform_keyword=Canada)'s Bombardier and France (http://www.wtopnews.com/?nid=733&inform_keyword=France)'s ATR, have ramped up production to 140 of the planes this year, after making 100 deliveries in 2007. This compares with only 26 in 2002.


It seems passenger comfort is moving down the priority list and fuel efficiency & airport restrictions are up.
http://www.wtopnews.com/?nid=111&sid=1370946

At highest density seating, it's only really a competitor to the A319 and shorter B737s. This will limit the market.

The Turboliner is inbetween the A319 and A320 and 737 and 738. A huge market.

http://www.boeing.com/commercial/cmo/images/lg_new_deliveries_cmo07.gif

Rooftop windows? Why? It's just another hole in the pressure hull and will add to the cost.

I took the A320/737 window arrangement as a starting point and removed 20% / 12 windows and places 4 rooftop windows. ;) I think natural light in the cabin could improve cabin admosphere / space perception while reducing weight.

It'll never be accepted by the fare paying customer, aka, the passenger.

I flew from LCY last week. Apart from BAE 146, props were the dominant aircraft; F50s, ATR, Saabs and Q400s flying under flags of airlines like SAS, KLM, LH, BA Swiss, AF. I have the impression pax were fare paying, or at least their bosses. :ok: http://www.youtube.com/watch?v=hY5TueMRq0k

I think for medium ranges the props miss speed (although new props are speedier) and capasity / ceiling. However there are many areas in the world where the majority of flights is under 700 nm and cargo unimportant. Western Europe isn´t the only place. Heavy 737/A320 are "mis-used" there. Look at the route structures of the low cost airlines.

http://i191.photobucket.com/albums/z160/keesje_pics/Turbolinerperformancerange.jpg?t=1206342271

In history engine developments played a major role shaping aircraft / route structures. I think the TP400 offering power / efficiency never available in the West, combined with skyrocketing fuel prices might lead to new configurations. http://www.youtube.com/watch?v=h-V5jzSslZo

[chornedsnorkack]

Remember: a new big turboprop is not competing with A320/B737 (which are not replaced till 2020). It is competing against C-series geared turbofans.

As for speed - why 676 km/h? I think A400 is faster (slightly). Tu-114 is fast, too.

If you start the design of, say, ATR102 from two big turboprops of Ai-400 (with counterrotating props) - what would be your suitable MTOW?

As for skylights, remember that Tu-134 has the skylight in a toilet...

[keesje]

Remember: a new big turboprop is not competing with A320/B737 (which are not replaced till 2020). It is competing against C-series geared turbofans.


Hi chornedsnorkack. I think a fast 150 seater for regional services is A320/737 territory. I think the C-series is a bit smaller and probably longer range. Not a typical short haul people mover.


As for speed - why 676 km/h? I think A400 is faster (slightly). Tu-114 is fast, too.


You might be right. I estimated conservatively on this one, a bit faster then the Q400. I selected a "fast wing" based on the E190 and tried to limit frontal area as much as allowable for short range 6 abreast. Maybe someone can make a better speed estimation.

If you start the design of, say, ATR102 from two big turboprops of Ai-400 (with counterrotating props) - what would be your suitable MTOW?

I took the BEA146 and TP400 as starting points & then adjusted everything within the boundaries of a engine failure at V1 at LCY (expect hor. stab.) I think if you make the 4 abreast ATR longer it would become very heavy to make it stiff enough. Long landing gears would be required too.


Tu-134 has the skylight in a toilet...


:confused: Is that so ? Anyone a picture of that? I remember the P3C had them, but obviously not only for fun / admosphere..


Built in powerpushes have been looked at before. The weight penalty doesn't make them attractive. besides, if it's a turboprop - why not give it the ability to reverse using the engines?


I think new and powerfull electric engines are changing the business case. Airlines are investing (Delta), suppliers taking strategic positions. http://www.wheeltug.gi/index.shtml .

Lets remember moving around airports on engine power / with help of tugs is not for free at all.

Noise, polution and fuel consumption (weight) during airfield operations are high & airlines are looking for solutions / improvements. Imagine how quiet gates / taxiways could become. Maybe more flights at difficult hours would become allowable / feasible.

Short haul operations can include up to 14 airport movements a day per aircraft. Air Pollution is starting to limit growth in many places.

[Raving RHAG Muncher]

Could GRP and Carbon Fibre be introduced to parts of the airframe to reduce weight? Flying controls, for example?

Is this feasible at these speeds? I think the Harrier makes use of composites, so it must be, I guess?

[TeachMe]

I live is Seoul and noticed that your range out of Hong Kong would reach Seoul. That got me thinking....

I have been flying around Asia for 12 years for work. Seeing a 737/320 is much less common at most airports compared to back home. I went to Vancouver last month and took a turbo prop to Kelona. Ohh what a cute little plane, and Vancouver had so many small planes (737/320s) sitting around and coming and going - neat!!

Small planes might work in the other markets you noted, but due to population dencity and oceans, which mean driving is less an option, bigger planes are relativly easy to fill even on shorter runs.

Out of about 30 flights in and out of Hong Kong, I have only flown 330s, 747s, and 777s to my recolection. The plane you suggest might work within China, say Xian to Nanjing, or in Thailand from Bangkok to Changmai, or from HK to small Chinese cities, but not much else.

However, it looks cool and I would love to fly it as a SLF. So, thanks for the idea. Your drawings are always quite interesting.

TM

[keesje]

Could GRP and Carbon Fibre be introduced to parts of the airframe to reduce weight? Flying controls, for example?

Is this feasible at these speeds?

I think composites / CRFP are not the perfect choice for every use. Looking at recent aircraft developments control surfaces, wings, wing torsion box, tail could be made in composites. Fuselage for these aircraft is a different question. Ramp rash and CRFP for fuselages don´t go very well together on aircraft that spend most time on busy airports.

Small planes might work in the other markets you noted, but due to population dencity and oceans, which mean driving is less an option, bigger planes are relativly easy to fill even on shorter runs.

Thnx TEACHME for your comments. I think the current generation of turbo props (ATR 72, Q400, F50) are more then twice as small as this Turboliner. It could offer turbo prop efficiency (-20% fuel etc.) at narrowbody 737 and A320 capabilities. Props have better airfield performance and fuel consumptuion below 450 mph. http://www.thestar.com/Business/article/350137

I projected a person to show how large it is compared to existing props. It is a A319 /737-700 sized 150 seat aircraft.

http://i191.photobucket.com/albums/z160/keesje_pics/turbolinermancomparison.jpg?t=1206367696

Out of about 30 flights in and out of Hong Kong, I have only flown 330s, 747s, and 777s to my recolection. The plane you suggest might work within China, say Xian to Nanjing, or in Thailand from Bangkok to Changmai, or from HK to small Chinese cities, but not much else.

My reference are European and US flights. Hundreds of narrowbody aircraft flying 4-10 daily connections on 500-800 nm city pairs. O&D as well as feeder flights. Then there is the booming low costs business. Almost all 150 seaters at short high frequency flights.

[Dan Winterland]

Hong Kong to Seoul is best served by a 747 or an A380. Max capacity counts on this high density route. And flying turboprops out of HK won't make you popular with anyone. Everyone needs to be doing at least 300 knots. It's pretty busy!

[chornedsnorkack]

Hi chornedsnorkack. I think a fast 150 seater for regional services is A320/737 territory. I think the C-series is a bit smaller and probably longer range. Not a typical short haul people mover.

C130 has maximum seat capacity of 145 at 5 abreast, MTOW up to 63 tons or so - bigger than A318, and closer to A319. The 64 ton version has 5000 km range - there is a version with 3300 km range and a lower MTOW.

So, C150 could be an option.

Is that so ? Anyone a picture of that? I remember the P3C had them, but obviously not only for fun / admosphere..

Well...
http://www.pixel-area.com/Demo/Blueprint/Plane/civil%20transport/Tupolev%20TU%20134.jpg

In the tail, above the engines.

Hong Kong to Seoul is best served by a 747 or an A380. Max capacity counts on this high density route.

747, with the exception of 747SR models, is too much of a plane for the range. Ditto about A380-800. Cathay Pacific said that they will buy A380 if Airbus increases MTOW OR stretches the plane. So, CX could use an Airbus 380-900SR in addition to their B777-300 non-ER...

[speedrestriction]

With props of that diameter I can see there being problems with tip speeds unless they are turning very slowly.

[Will Bored]

Looks like someones university project to me,....... less prop in the sky, more Pie in the sky!!

Will

[keesje]

With props of that diameter I can see there being problems with tip speeds unless they are turning very slowly.
I think the original spec was 655 rpm for the low attitude cruise, 730 rpm during normal cruise and about 842 rpm at take-off. Maybe this will be adjusted. The TP400 is a combination of new technology & unknown territory in terms of size and power (vibrations, torque, gearboxes, etc).

Over 1000 ground hours have been done on the TP400-D6. The delayed first flight on a Marshall C-130 will take place soon (hopefully) after ground runs / tests.

http://www.flightglobal.com/assets/getAsset.aspx?ItemID=21559

Could a friendly moderator shift this to spotter's corner please?

Beacon, that seems an unlogical place for this thread. It´s only a concept.

[Dani]

We don't need research in airframes if it's a propulsion problem. First we have to get the unducted fan techology, then we can go on with delopping the aircraft.

So far, unducted fan didn't work, and there wasn't enough positive feelings from the customers.

But, there are promising projects in the pipeline. So let's wait and see.

Dani

[keesje]

We don't need research in airframes if it's a propulsion problem. First we have to get the unducted fan techology, then we can go on with delopping the aircraft. So far, unducted fan didn't work, and there wasn't enough positive feelings from the customers. But, there are promising projects in the pipeline. So let's wait and see.

Dani this is not an unducted fan. The TP400 engine has been under development by Rolls Royce, Snecma, MTU and ITP for years. It was run first in 06 and will take to the skies in a few months. First 4 engines for the A400 prototype have been delivered earlier this year. It is not proven in service yet, but it isn´t a concept either.

http://www.flightinternational.com/assets/getAsset.aspx?ItemID=10672

In this case an the engine is there, it will enter service on the quad A400M transport aircraft. The Turboliner would use 2 TP400s.


C130 has maximum seat capacity of 145 at 5 abreast, MTOW up to 63 tons or so - bigger than A318, and closer to A319. The 64 ton version has 5000 km range - there is a version with 3300 km range and a lower MTOW.

So, C150 could be an option.


The concept TurboLiner is optimized for routes up to 2-3 hours. Narrowbodies like the 737/a320 can do 5-6 hours and cross the Atlantic with a few additional tanks. Penalty for this flexibility / capabilities is addition structure everywhere & weight.

The 737 / A320 weighs empty about 40 tonnes. The Turboliner would weigh under 30 tonnes. Those 10 tonnes equal 100 passengers..

http://i191.photobucket.com/albums/z160/keesje_pics/Turbolinerconceptsoverview-1.jpg?t=1206483067

[Dan Winterland]

Quote:
Hong Kong to Seoul is best served by a 747 or an A380. Max capacity counts on this high density route.

Reply:
747, with the exception of 747SR models, is too much of a plane for the range. Ditto about A380-800. Cathay Pacific said that they will buy A380 if Airbus increases MTOW OR stretches the plane. So, CX could use an Airbus 380-900SR in addition to their B777-300 non-ER...

747s are used frequently on the HK Seoul route along with Manilla, Taipei and several other short range high density routes in Asia. What counts is lots of seats. JAL use the 747-400D between Tokyo and Osaka. 600 seats, no galleys, 40 minute sectors.

Now a passenger A400 with 500 seats on two decks might work!

[chornedsnorkack]

JAL use the 747-400D between Tokyo and Osaka. 600 seats, no galleys, 40 minute sectors.

Really?

I think the largest seat count I´ve heard of was 594, in Japan, and I understand it no longer flies. Currently the biggest plane in the world is the 747-400 of Corsair - with 587 seats. And they have long sectors (what about galleys?).

Oh, and technically propeller planes should be easier to stretch than jets. Low cruise Mach should allow thick, unswept wings, which would offer better resistance to bending and twisting at less structural mass. How would a Brabazon wing compare to an A380 wing?

[keesje]

For illustration, compared to existing props the Turboliner is longer wider and faster. Compared to A320 series smaller and lighter. It lacks the container / palet capability of the A320 family and its roomy cabin.

I think together with its semi rectangular fuselage the Turboliner offers just enough width to allow acceptable comfort & stowage for sizeable hand luggage for short haul flights.

The A319s have a wider cabin & belly haul and are able to carry 150 passengers and a healthy cargo load to level 40 quickly, go Mach 0.8, fly over the weather and put everything down 5 hours / 2500nm later. A different requirements but you pay the weight on short passenger operations like e.g. Low Cost Carriers.

Current regional props are better for ground operations, short runways, steep approaches and low fuel consumption but lack speed, climb and capasity.

I think the TurboLiner could combine capasity, fuel efficiency & airfield performance in a noise restricted environment.

http://i191.photobucket.com/albums/z160/keesje_pics/Turbolinerpropcomparison.jpg?t=1206540678

-> Anyone know what ATR, Europrop and worn BAE146 operators are thinking about the future?

-> I have seen figures on airport environmental pollution by ground moving / waiting aircraft somewhere, does anybody know where to find this info?

[Max Angle]

Seems to me that what Airbus reallt need is something to fit in between the A321 and the A330-200. At the moment there is a big range/payload gap which we are having to fill with two leased 757's. A310 is now out of production and there seems to be no replacement planned.

[keesje]

Seems to me that what Airbus really needs is something to fit in between the A321 and the A330-200. At the moment there is a big range/payload gap which we are having to fill with two leased 757's. A310 is now out of production and there seems to be no replacement planned.


Max Angle I think you are right. Last year I came up with some ideas in a different thread. Real A300, 310, 757, 767 replacement aircraft idea http://www.pprune.org/forums/showthread.php?t=303170&highlight=keesje

I think it is telling how many carriers decided to introduce their older 757s on the Atlantic in the last few yrs. BA, UA, AA, NW, US, DL.. but thats the other thread. Feel free to add aditional comments / ideas there.

[keesje]

Guys, you are making it too easy on me. I didn't want this concept to be trashed & laughed at but a some constructive comments are more then welcome..

http://i191.photobucket.com/albums/z160/keesje_pics/Turbolinerdimensions.jpg?t=1206708910

Some improvements I think have yet to include (see current configuration above):

Prop - fuselage clearance is large in relation to the size of the vertical stabilizer. Moving the props closer to the c.o.g & reshaping the stabilizer would improve handling during an engine failure at low speed (V1) I think. I'll check what the clearance will be at the A400M & how the vert. stabilizer size compares to other twin props..
Landing gear in the side view is more of the vertical retracting kind. For a aircraft this size it would require a lot of structure / fairings to accomplish a wide enough wheel base. Better adjust it to the more realistic type as can be seen in the front view (e.g. BAE146).
Vert. stab. dissapeared in top view (graphic typo)
Airbrakes. I think aircraft like BAE146 and F100 really benefit from those during steep approaches, any experience? (APU sits in the way though..)Any comments / ideas to make this concept better / more realistic?

Hinged wings outside of the flaps starting inbetween flaps with the flaperons, any thoughts? Think of the total center wing including engine mounting as one big, composites, stiff section.. combined with electric drive it could park anywhere and create a lot of space / better density on restricted airports (LCY).

Thnx in advance !

[erikN]

I'm sorry that I can't help you with improvemenst or any feedback but I think you got a really nice project going on and some good ideas.

[keesje]

Thnx erikN!

I changed the Turboliner a bit


The engines are placed closer to the fuselage to improve asymmetric thrust stability during one engine out situations. The vertical stabilizer is enlarged / reshaped for the same reason.
Landing gear doors and vertical stabilizer have been corrected from the earlier drawing
Biggest change: cross section. I think the cargo belly was unnecessary large for the foreseen use of such an aircraft : short range flights to busy places. Cargo is unimportant here and people prefer hand luggage over check-in luggage. The floor was lowered enabling the luggage bins to be enlarged and the lower fuselage was flattened, resulting in a further reduced frontal area ( lower drag) and more space in the cabin.
The APU Silencer was smoothened out and speed brakes added to assist in steep approaches reducing acoustic footprint in populated airport areas.
Seat count was increased by 6 seats to 168 in single class 6 abreast, by reducing the seat pitch from 32 to 31 inch. No need to get spoiled :=.http://i191.photobucket.com/albums/z160/keesje_pics/TurbolinerImprovements-1.jpg?t=1206828023

I think this aircraft would be aimed at the <800 nm market replacing 737-300, A319, BAE146, F100, 717, MD80 and other aircraft used in these markets. Ryanair (and e.g Clickair :eek:) would put in a few more seats..

Other technical details would be:

Fly by wire
Sidestick (creating room in relative small cockpit)
Advanced gust elevation & noise reduction for passenger comfort
Glass cockpit, low nose, dual HUD for better situational awareness
Two entrance doors with integrated stairs which together with the self towing capability help reduce turnaround times and ground support dependability.

[Lemurian]

Keesje,
I've followed this for a while and I have a few questions :
1/- Why the leading edge flaps ? The #1 behind the props seem to be both an overkill in terms of aerodynamics, weight and dimensions ( they are also subject to the prop wash). I would have thought that the wing behind the engines will already be in a good lift-generating position.
2/-the shoulder wing choice : as a pilot, I've loathed the crosswind susceptibility of airplanes like the Nord 262 or the ATR, because of their narrow landing gear. See the balance of weight savings on a comparison between A/- structural gains in getting away from the project as it is now and B/-the advantages of a low wing, wide landing gear, wing bending moments...etc...
Another advantage of the low wing is the easier integration of the airplane with existing airport gates - that will allow you to do away with at least one integrated airstairs, hence a further weight saving.
Lastly, the fuel system would be simpler, with the added possibility of a centre tank.
Just my two euro cents.

[low n' slow]

My 5 Cents.
Being the pilot of a flying snowball, I welcome the idea of a bigger, better TP.
I like the design! But make the nose looke a little more like the Saab and less like the Dornier and you're home free!

It's all very nice with the electrical tug system, but I feel it will function just as all the other "nice to have capabilities" I have so far seen, and that is occasionally/sporadically. Having complex electronics in an area that will take up a lot of force in everyday operations just doesn't feel sound to me. Reliability and ease of maintenance is very important and any factors compromising this must be taken into consideration.

Also I feel a little sceptic to the gear/wing configuration. It would feel more sturdy having the gear in the nacelles (Fokker and Dash) instead of the ATR-type placement. A high wing I argue will make the plane more sensitive to strong crosswinds.

I also notice you have given the plane speedbrakes similar to the Bae. You would save more just getting rid of them. Remember, it's a turboprop. Not only are they inherrently slow, but they also have a fantastic stopping capability by means of the props... Having liftdumpers/flight spoilers though (Dash) makes a little sense considering manouverability and landing the wing upon touchdown.

By the way, what is all of this for? Looks the buisness, can't be just for fun or is it?

/LnS

[Bald_Eagle]

Hi,

Nice design but why the need of an apu? Saving weight and space by using hotel mode....

greetzzzz

[low n' slow]

Hotel mode is very hard on the engines, plus it is very very noisy. I agree that an APU is the better option...

[keesje]

Hello thnx for all comments / ideas / insights sofar!

Some have commented on the landings gear, should it be located in nacelles.. I have to find out how long they would have to be for a high cabin / big prop. With the required strenght / stiffnes they could become very heavy..

Other comments on the wing location, it could be higher on the fuselage to stay out of the cabin (important for a suggested freighter version), like An-32..

http://cdn-www.airliners.net/photos/middle/4/0/8/1331804.jpg

If I have a little time I will list all your suggestions, make trade-offs and incooperate them in a mark III versions.

Please stay tuned / keep your comments / ideas coming to improve the concept.

thnx & rgds
keesje

[kiwilad]

Keejse,

Very interesting idea. Not sure how hard hotel is on the engine, the ATR seems to do alright, is a lot lighter than an APU.
Some of the problems with it in the ATR sense are you can not refuel with hotel running. It is limited to only 10kts tailwind, and dependent on wind direction we have to turn the bleed off to stop the exhaust gas being sucked in.

If you do go with the apu, something that you can leave running unattended would be great. As I understand most props with apu's require someone on the flightdeck or at the least in the cabin as they don't have automatic fire extinguisher capabilities. I stand to be corrected.

Have you dug around for info on the ATR 92 concept that is on the drawing boards at ATR at the moment. The Q400X is another one in concept at the moment. I personally think the ATR concept is better as it will be a clean sheet design, with a gear design similiar to yours.

I agree with a earlier comment about crosswinds, the problem with the ATR is the wing continues to fly to around 40-50kts, spoilers that dump lift on landing would start to solve some of the issues surrounding the interesting crosswind handling techniques.

Look forward to more concept ideas.

Cheers

[keesje]

I'm not sure if Hotel mode generates enough energy for the electric drive.

The aircraft is supposed to push back & taxi without the main engines (props : noise) running as illustrated in the first picture.
http://i191.photobucket.com/albums/z160/keesje_pics/Turbolinercomponents.jpg?t=1207130960 The engines would be started at a TBD time and place close to the runway. Arrival the same: engines out after leaving the runway.

Idea is electric drive would ease environmental concerns / restrictions but also ease push back requirements, even allowing a certified cabin crew member to perform it, boarding the aircraft by airstairs after ground control approval..

[an3_bolt]

Congrats for thinking laterally.

As others advised previously - pax appeal for a turboprop is not as great as a jet. But the economics......

By the way the unducted fan (UDF) did actually work and worked quite well. Refer http://www.flightglobal.com/articles/2007/06/12/214520/whatever-happened-to-propfans.html and maybe another that might lead you to more details http://pdf.aiaa.org/preview/1987/PV1987_1733.pdf

Perhaps a rear mounted UDF similar to the MD80 test might have a greater appeal.

[Bald_Eagle]

Might have posted a little bit hasty :ugh: Recognising APU would be far better...

Since the idea is to taxi WITHOUT the main engine running by means of an electric drive.

Beside that hotel mode seems to have some major disadvantages, as some pointed out: safety issues (prop bake / hot exhaust gases), noise, wind lim. and engine wear.

Nevertheless ATR believes strongly in this system:

Why ATR has not developed an APU for its aircraft?

“ATR offered an innovative alternative to the APU known as the "Hotel Mode". The Hotel Mode concept (i.e. offering air conditioning and electrical power on the ground) was made possible through the application of a propeller brake on the right hand side engine turbine. Thus the weight and added maintenance cost of an APU is spared.
A survey of 20 customers (214 a/c) has been made to gather information about the rate of utilization and the effectiveness of Hotel Mode. The data gathered from ATR Customers have confirmed that Propeller Brake installation is a smart and effective solution welcomed by Airlines due to tangible advantages over APU.

[kiwilad]

An_3, you may be right about the pax appeal of jet vs props but I have not come across a travel/booking website which gives you the option of choosing which aircraft type you can fly on. Most give the price option, then the date specific option. If you did want to fly only jet it would take a fair bit more digging to find out.

We fly CHC-WLG vs B737, they pass us in the climb/cruise/descent, but generally we are pulling up on the gate in the ATR about the same time as there passengers are getting up out of there seats. No more that 10mins in it, and pax do prefer the ATR as door to door it is debatable who is quicker, no security checks, quicker boarding and deplaning, and they get a cup of coffee as well.

If Cook get a different type Q400/ATR92, then it will be just as quick if not quicker. As airspace gets more congested for NZ standards, speed control increases and jets on short sectors are only really gaining in the cruise, sometimes in the climb and descent, but if they are above us, there is sometimes not the distance to run to get them thru infront. We can go 250kts to about 8nm final, so we get to catch them up near the end a bit.

Keesje the ATR in Hotel mode is supplied by the same engine driven generators so can supply normally 400A DC.

My 10cents worth.

[keesje]

By the way the unducted fan (UDF) did actually work and worked quite well.
an3_bolt, thnx. Indeed there is renewed interest in UDF. I think UDF are a bit further awaythen e.g. the TP400. Noise / resonance / gearbox cooling / mechnical complexity need time to sort out. Still in the background I have been working on something UDF above 200 seats with Henry Lam, stay tuned..


Might have posted a little bit hasty..
......
Nevertheless ATR believes strongly in this system:


Bald_Eagle, thanks for your input. I doubt a system based on Hotel mode would be able to take a slope / bridge at MTWO and maintain a speed of 20 mph over longer taxi times. The Turboliner would be much heavier then an ATR too.

Keesje the ATR in Hotel mode is supplied by the same engine driven generators so can supply normally 400A DC

Kiwilad, thnx. I took a closer look at the TP400. Its a big 3 shaft engine. It has a dedicated microturbine starter integrated that needs limited power to start itself. http://www.microturbo.fr/article.php3?id_article=181&lang=en. It weighs 15.5 kg.

I think an APU optimized for moving the aircraft around could be equally limited in size and weight. Its doesn't have to produce the bleed air to start up a big turbo fan engine. An serious effort to really reduce noise to a minimum by means of a silencer would add some weight.

Your experience on flying ATR versus 737 on short routes confirms my airline experience. The shorter the flight the less difference between gate to gate times between props & jets. Props are often allowed to use secondary runways too.

This week-end I'll try to summarize & do a Turboliner mark III based on all input

rgds

[an3_bolt]

Can't wait to see the UDF concept.

I firmly believe if you can come up with a M0.75 - M0.77 @ 30,000 UDF you will have a winner - especially if it is rear mounted away from the interference with a super critical wing using a counter rotating design to remove swirl effect. Something along the lines of the GE36 UDF might be workable (although a little small for you as suitable more for the 100-160 seat range) Side benefit is lower cabin noise, high propulsive efficiency and excellent specific fuel consumption.

Might need some good software or access to a wind tunnel for optimum location free of interference/other airframe effects at all AoA.

I am sure your fresh lateral thinking is going to take you a long way.

Cheers.

[enicalyth]

All my research and that of my colleagues is published in the leading journals. But you have to buy it. It is not free.
But reasonable. It is a shame you are not using it.

[Bushfiva]

Regarding the overhead storage, we're always being told what the maximum size is. And with loco's we're being educated that you're a burden for bringing checked baggage. On the third hand, one of the problems with this type of aircraft is that one can board with a carryon-sized item for which there is no longer any space. So my suggestion is, a check-in - side check that one's roller case is the correct size, which gives one a chit for an overhead slot on the aircraft. It doesn't matter when you board, that slot will be there. Those with the random-sized packages get to stuff them below the seat in front. One would receive a boarding pass with a seat number and baggage slot number.

[keesje]

Hello folks,

I promised to do an updated mark III based on all your input last week-end. Kids & home improvement caused a small delay. I went through the comments and implemented some suggestions .

Result is the Turboliner Mark III


1. lemurian
Why the leading edge flaps ? The #1 behind the props seem to be both an overkill in terms of aerodynamics, weight and dimensions ( they are also subject to the prop wash). I would have thought that the wing behind the engines will already be in a good lift-generating position.

True I took the Embraer 190 wing as a startingpoint. I removed the leading edge flaps on mark III. Ice protection plates are now situated behind the prop.


2. lemurian
The shoulder wing choice: as a pilot, I've loathed the crosswind susceptibility of airplanes like the Nord 262 or the ATR, because of their narrow landing gear. See the balance of weight savings on a comparison between A/- structural gains in getting away from the project as it is now and B/-the advantages of a low wing, wide landing gear, wing bending moments...etc...

3. low n' slow
Also I feel a little sceptic to the gear/wing configuration. It would feel more sturdy having the gear in the nacelles (Fokker and Dash) instead of the ATR-type placement. A high wing I argue will make the plane more sensitive to strong crosswinds.

I took a long & hard look at gear in the nacelles. To keep the size of the main landing gear within a reasonable envelope it becomes necessary to make the fuselage as flat as possible like on An32, Q400 and F50. This aircraft is meant to replace 737 and A320 on shorter legs. Also leisure / low cost flights where people take a lot of luggage. Doing a Google on Q400 and luggage I found a lot of complaints. It is a major restriction on this aircraft caused by the aircraft cross section. The Turboliner doesn’t have to have cargo container / pallet capability like the A320 and I did flatten the lower fuselage. However it has to have enough space to stow 160 serious bags. This would result in a very long and heavy main landing gear. Also including electric drives on it could create issues. So I decided to stick with the ATR / military style landing gear. I included the Q400 cross section for reference in the drawing.

http://i191.photobucket.com/albums/z160/keesje_pics/TurbolinerIIIdimensions.jpg?t=1207784589


4. lemurian
Another advantage of the low wing is the easier integration of the airplane with existing airport gates - that will allow you to do away with at least one integrated airstairs, hence a further weight saving.

Having the very large prop would create some ground clearance issues requiring very high main landing gear legs. I did a lot of different studies and in the end concluded a high wing isn't so bad for a prop. ;)


5. lemurian
Lastly, the fuel system would be simpler, with the added possibility of a centre tank.

True for narrowbody aircraft, but they can do flights up to 3000nm. The Turboliner is an uncompromised short haul aircraft, mostly up to 1000nm. I think the long un-interrupted wings would provide enough space for its limited payload range requirements.
http://i191.photobucket.com/albums/z160/keesje_pics/turbolinermarkIIIspecifications.jpg?t=1207784686


6. low n' slow

Make the nose looke a little more like the Saab and less like the Dornier and you're home free!

:-) I see you have a national preference. I drew the nose low to maximize the viewing angle for the pilots. This aircraft is driving over airports a lot during the day.


7. low n' slow
It's all very nice with the electrical tug system, but I feel it will function just as all the other "nice to have capabilities" I have so far seen, and that is occasionally/sporadically. Having complex electronics in an area that will take up a lot of force in everyday operations just doesn't feel sound to me. Reliability and ease of maintenance is very important and any factors compromising this must be taken into consideration.

The assumption is the silent aircraft will be allowed to operate where noise restriction are important. Fuel will be saved by running the APU instead of two engines and not requiring push back tugs.. (less lost slots too I guess..)


8. low n' slow
I also notice you have given the plane speedbrakes similar to the Bae. You would save more just getting rid of them. Remember, it's a turboprop. Not only are they inherrently slow, but they also have a fantastic stopping capability by means of the props... Having liftdumpers/flight spoilers though (Dash) makes a little sense considering manouverability and landing the wing upon touchdown.

9. kiwilad
I agree with a earlier comment about crosswinds, the problem with the ATR is the wing continues to fly to around 40-50kts, spoilers that dump lift on landing would start to solve some of the issues surrounding the interesting crosswind handling techniques.

I removed the speed brakes. I installed a patented (Lockheed) system called DLC (direct lift control). In combination with other control surfaces & black boxes it allows to decent without changing pitch or engine settings. Gliders have something similar and Lockheed used it on the L1011 Tristar. For an high winged aircraft doing steep approaches up to 8 times a day, its seems very useful interms of comfort and limiting noise (no engine thrust variations). During landing they act as additional spoilers.

http://i191.photobucket.com/albums/z160/keesje_pics/turbolinermarkIIItechnology.jpg?t=1207784756

10. kiwilad
If you do go with the apu, something that you can leave running unattended would be great. As I understand most props with apu's require someone on the flightdeck or at the least in the cabin as they don't have automatic fire extinguisher capabilities. I stand to be corrected.

If it is allowed it should be possible. It is a relative small and high placed APU.

11. kiwilad
Have you dug around for info on the ATR 92 concept that is on the drawing boards at ATR at the moment. The Q400X is another one in concept at the moment. I personally think the ATR concept is better as it will be a clean sheet design, with a gear design similiar to yours.

I could not find sketches, do you have any links? :confused:


12. Bushfiva
Regarding the overhead storage, we're always being told what the maximum size is. And with loco's we're being educated that you're a burden for bringing checked baggage. On the third hand, one of the problems with this type of aircraft is that one can board with a carryon-sized item for which there is no longer any space. So my suggestion is, a check-in - side check that one's roller case is the correct size, which gives one a chit for an overhead slot on the aircraft. It doesn't matter when you board, that slot will be there. Those with the random-sized packages get to stuff them below the seat in front. One would receive a boarding pass with a seat number and baggage slot number.

I have experienced this issue with regional jets often. I think the Turboliner offers handluggage space comparable to narrowbody jets (cross section is narrower but rectangular).


13. James (Fleetbuzz)
Some details which become apparent include that the wing box will conflict with the overhead bins. The fuselage cross-section is similar to a typical low wing aircraft and would be slightly different in a high wing aircraft. In a low wing aircraft the cargo bay is the natural location for the wing box to intersect the fuselage. In this high wing aircraft the thin side-walls will not be enough between the wing box and the landing gear and also have a cut-out for an emergency exit at the same time. There is a lot of load in the frames especially in the area between the rear spar and the landing gear.

The wing box may limit headroom unless the wing is located higher on top of the fuselage. High enough to allow headroom, overhead bins, and for a cargo version an unlimited cargo volume. Also the fairing around the landing gear and the wing to fuselage would be much bigger to smoothly cover the box and gear. One benefit of the larger fairing is it allows for structural supports and some system components to be located outside of the fusealge skin under the fairing. External structural features under a fairing are more efficient so the designer will use them whenever possible as soon as the fairing is deep enough to allow them.

I took a look and you seem to be right. I heightened the wing a bit, it comes into the cabin / bins. The fuselage height in the lowest point of the aisle should still be better then 2.1 meters (it's a big cabin for a prop.) Height is about similar to the BAE146 only Turboliner cross section is more rectangular shaped.


14. James
Early design decisions include arranging the structure to allow for a side cargo door and sizing the cabin for standard containers. A swing nose or tail would allow full access to load cargo but may be too complicated. Swing nose/tail has only been used on very specialized aircraft.

I think a conventional side door would be sufficient for typical short haul parcel loads, like the BAE 146 Quiet Trader..


15. James
A high wing may end up with the slight dihedral shown in the illustrations and the vertical stabilizer looks almost big enough to react a one-engine-out yaw. The top of the vertical stabilizer would also need a fairing big enough for the screw to adjust the horizontal stabilizer pitch trim. Also the aft fuselage may be longer/forward fuselage shorter to react the weight of the engines forward of the wing.

The mark II had your concerns covered. I think the place of engines, wing, tail and the fuselage length is pretty accurate. I measured many top views of twin props for reference.Of cause I could have made a spreadsheet estimating all weights & load arms and determine the Lift locations but decided someone else might want to pick up that challenge.. ;)


16. James
The wing box may need to be thicker to take the engine loads. Try to avoid the limited life problems seen on the C-130 and P-3; easier said than done. A thicker wing immediately impacts the cruise speed....and many, many other design parameters all of which influence each other.

A thicker wing box has consequences for the aerodynamics high speed performance of the wing. I think it should be a CRFP wingbox. There would be indeed serious loads from the big engines and long fuselage.


17. James
If the overhead windows are to allow light in the cabin to save exectricity for cabin lights, then the windows should be minimal in size and make use of a reflector/diffuser and not make a hole in the fuselage any larger than necessary. Side windows are subjected to pressurization and shear loads, the top of the fuselage also has bending loads in either tension or compression and a large window may have a weight penalty.

I made the drawing a bit clearer, small windows indeed and brackets to take the loads. The 4 overhead windows came in place of 20% / 12 windows deleted in comparison to the A320/737. It is mainly a weight reduction combined with a better space experience / admosphere for people sitting in middle / aisle seats.

18. James
It remains to be seen if the TP400 lives up to it's potential in-service. An excellent engine design that delivers the fuel burn and thrust can still fail if it costs too much to maintain.

The Turboliner should become available years after the A400M enters service. Child deceases could be engineered out of the TP400.

19. James
Composite fuselage?

Personally I have my doubts on CRFP for short haul, airport intense operations. Damage, ramp rash is a fact of live for an aircraft that does 6-8 flights a day.. Also not sure if layered composites and prop resonance go together well..

BTW I adjusted cabin for 6 more seats reducing pitch from 32 to 31 inch. (some low cost airlines I flew do 28 inch :sad:..)

http://i191.photobucket.com/albums/z160/keesje_pics/TurbolinermarkIIIcabin.jpg?t=1207785643

20. James
TP400 implies bleed air.

The TP400 use a microjet as a starter. I hope this could limit the size of the APU and save a lot of piping.

21. James
Props can shed ice of there is usually a reinforced skin next to the props.

Indeed. I included protection plates behind the props like most turbo prop aircraft have.

22. enicalyth
All my research and that of my colleagues is published in the leading journals. But you have to buy it. It is not free. But reasonable. It is a shame you are not using it.

I have no reference, may you could lift a tip of the curtain / provide some keywords?


23. James
A clever design will address the issues with solutions which solve multiple needs at the same time and do it with elegant simplicity. The 777 would not exceed performance specs unless it included very clever design solutions.

I would be interested in hearing any other comments on the design details implied by this configuration. The details help clarify the accuracy of the overall performance analysis so as to avoid overestimating.


Agreed, any comments / ideas are welcome!

[mcgnuggitt]

I am a believer in the future of turboprops.:D
The theory of "turboprop avoidance" is sheer myth. Besides, people will fly any equipment, provided it meets their schedule, price and preferably DIRECT routing. Recently in Toronto, Porter has been a booming success!

Only turboprops have the economics to do this task going forward. Jets, like RJs have had to get bigger and bigger to maintain economic leverage. Turboprops, with a slight speed push, can replace jets on many routes. You only have to look at Horizon canceling CRJ00 orders in lieu of Q400s, Luxair refleeting their EMB145s with Q series...ATR can't accomplish this as they don't have the scoot of the Q400.

So, I love the highspeed high cap concept you have. I agree you'd need to push over M.7 tho..the P3 has a max of 400kts, and the Q400 is only 360, you should hop up the speed on this.
Also, pax HATE entering the AC from the rear and it reduces the chance of boarding with Jetways.

As far as bringing IN teh engines...bad call:=. By bringing the props close to the fuse, you're inviting a larger blade pass vibration as the blade tip shockwaves won't have time to abate. Keep them away from the fuse or you'll end up with a noisy shakey fuse. IMOHO

Anyway, this look alot more than just a hobby to you...where'd you do your design training?

[mcgnuggitt]

I've heard of ATR mulling over a clean sheet..but haven't seen any concepts. I'd love to know more.

Being a KIWI flier, I'd bet you do some pretty steep aproaches (being mostly mountain out there)...and on that I know the Q's are better than the ATR. I wonder if the ATR92 will address that defficiency. That would allow a nice big turboprop to service the city centre airport here in Toronto and improve service to some of the busier destinations.

Any links to where I can see what they have on the shopping list?

[mcgnuggitt]

Even ATR is beginning to admit that Hotel Mode isn't very good. They've implemented in their -600 variant an electrothermal air conditioning unit to "supplement" hotel mode bleed powered cabin cooling. (Talk about adding weight!) You've gotta love how they spin this correction for lack of original performance as a wonderful enhancement LOL:E (Engineer's rule #2: If you can't fix it, call it a feature)

The APU on the Q series is much better than hotel mode, and DOES operate unattended. (unlike some APUs and Hotel mode).
ATR also put the hotel mode on the same side as the service entrance and fuel fill port. so no servicing can be done. So much for turnaround time at the gate. :ugh:
Sure, they cal Hotel time "ZERO ENGINE" time ...but the prop brake fails pretty often. (under 3000 hrs mtbf). I am pretty sure APUs last longer than THAT!

[kiwilad]

I agree that the APU maybe the more cooler method but part of that reason is that it can be left going for the whole turn around, hence has a longer period to try and cool the aircraft. In hotel, it needs to be shut down for servicing, fuel and unloading the rear of the aircraft. It is generally started only 5 sometimes 10minutes before departure so with a full load on a hot day it is already way behind trying to cool down a 30+C cabin. The complaints we get from the cabincrew the most is with a full cabin the air con struggles to keep it cool.

ATR92
I know a little about this only in the form that with our fleet soon to be up for renewal ATR have been briefing our managers on the replacement for the atr 500/600 which i think is to be designated the 700 (high70seats) and the atr92 (90+ seats). Both clean sheet designs.
Same general layout as the current atr but with a major change being that the baggage/cargo holds will be placed underfloor. Still the gear in pods from the fuselage. Passenger entry will be via a front door. Not sure if it is going with a prop brake or not?
The target design speed is a cruise TAS of 320-330, so I guess an indication that atr conceed a little more speed would be better.
Will incorporate all new A350/380 technoligies. Will have a new technology anti/de-ice system which won't require bleed air. Hydralulics will be individual power packs at each point which requires them. No central system.
I am pretty sure that it is going to be side stick, so fly by wire also.
Will try and find more out but there is nothing on the net yet as is all still concept and planning at ATR.

Cheers

[Lemurian]

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.

Your choice.

Regards

[mcgnuggitt]

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!)

[keesje]

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

[keesje]

Hello

I summarized everything in 1 slide. Changes:

counter rotating props
combined DLC / liftdumpershttp://i191.photobucket.com/albums/z160/keesje_pics/Turbolineraircraftturboprop-1.jpg?t=1208899184

rgds

[broadreach]

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.

:ok: 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.

[rubik101]

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?

[FireLight]

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. :ok:

[keesje]

broadreach


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 :ok:!


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!

In the name of pax safety, place the seats facing rearwards.

rubik101. Interesting idea:cool:. 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..)


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.

http://www.luxurylaunches.com/entry_images/0707/09/4_787windows-thumb.jpg
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? :confused:

rgds

[mcgnuggitt]

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!:D

[Lemurian]

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 ?

[cockney steve]

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?

Sorry if I'm talking crap! I'm not "in the trade"

[keesje]

Hi FireLight, mcgnuggitt, Lemurian, cockney steve, thnx for your comments. I'll take a close look in the week-end.


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.


Ecoflyer, ppropliner, cityhopper, ppropexpress, ropconnect, whisperliner, electroflyer , cityexpress, ecoexpress, ecopprop.. :\ any inspiration?

Just let it flow maybe trigger someone to find the right name..

[capster]

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!

[Masai]

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."

[keesje]

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..


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.

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.

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.

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)

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..

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.

http://i191.photobucket.com/albums/z160/keesje_pics/Turboliner28april.jpg?t=1209337856

Masai, thnx, haven't communicated outside pprune.

[Atreyu]

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...

Good work though!!

Atreyu:ok:

[Atreyu]

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. :eek:

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!!! :})

I watch with interest.

Atreyu:ok:

[broadreach]

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….”

[keesje]

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.

http://i191.photobucket.com/albums/z160/keesje_pics/TURBOLINERMAI2008.jpg?t=1210596604

Changes compared to earlier sketch:

Additional escape window (required)
Alternative simplified main landing gear
Wing - engine pylon fairing
Belly access doorsIt would be nice to have feedback from folks from fleet management departments / OEMS. What would be the best way to get their opinions?

[PETTIFOGGER]

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

[PETTIFOGGER]

Re Jstflyin, the Russians were quite good at it. Have a look at the IL 18 http://en.wikipedia.org/wiki/Ilyushin_Il-18 of 50 years ago. The oxygen mask argument which I have heard or seen before is a bit flat-earth, imo. I like Keejse’s design proposals, but I also like my comfort, and so do most people. Comfort costs money but is appealing to the customer and therefore good for business. The more that can be demonstrated the more likely someone will look seriously at such designs. Is it impossible to incorporate the comfort factor and keep down operating costs? Maybe. But on a much smaller scale Saab appear to be making a good job of it.
rgs P

[PK-KAR]

I assume the door will be >6ft above the ground when on the gate... if that's correct, then I think you'd need means to assist evacuation from the emergency windows (as there is no wing there). Given this, I think a smaller door (739 style) will be better to be put where the emergency exit windows are, or maybe move it clear off the sponsons... as you need a slide from the exit and you don't want it to get poked by the wheelbay door or landing gear mechanism.

Anyways, nice stuff Keesje, although I was wondering if someone would do a mini Tu114 twin... *grin*

[Mad (Flt) Scientist]

Some comments on the aerodynamic configuration, if I may.

Control System Architecture

Looks like the elevator and rudder are manual, or at best hydraulically-boosted manual. (Tabs on both surfaces, horns on the elevators). Yet the ailerons have no tabs of any kind, and you've got "high speed" ailerons, which implies to me a purely hydraulic solution for roll control. I don't think that's a consistent approach; you're going to have to build in a level of hydraulic redundancy to address the roll axis, so you may as well use the same systems for the other axes too.

I'm not convinced of the need for a "high speed" aileron option, nor am I convinced that not having spioilerons is a good choice.

I see no provision for ground lift dumping, other than the slightly oddly located "direct lift spoilers". Why are they so far forward - they are going to infringe on the fuel tank volume sat in the middle of the chord. Usually they'd go just ahead of the flaps so they could mount on the rear spar.

The h tail looks a bit small, as indeed does the rudder.

The wing isn't "dressed" so I'm guessing you're assuming artificial stall protection?

It looks like you've got AI protection only either side of the nacelle - with the new rules for icing that unprotected outboard wing is going to be a real drag, no pun intended. If you're going to leave the wing unprotected you'll need a big wing, and still may have problems.

The wing/body fairing looks too small, just by eye.

Re the emergency exits: maybe you can argue that the UC door is the step-down surface and avoid slides? Need to align the forward exit with the gear door in that case.

[galaxy flyer]

Hasn't the idea of Wheeltug" been done to death somewhere else on Pprune? Seems like a needless complication. But, the design does look promising.

GF

[airfoilmod]

Fascinating effort, just great. I like the DLC (from the 1011?) that mitigates the low level burbling. I think you're off base on the "wheeltug" concept, though. Anything that incorporates ground handling costs in favor of the Landing authority is not a good economic design. In other words, once my aircraft is on the deck, it's a truck. Airplanes are not good trucks (or tugs), and logically it is counter design to try to mitigate what is arguably the ground's duty. I would try to interest others in building new tug designs, vehicles that are more versatile and can be designed to travel (while towing) greater distances. If you look at the cost of carrying around (wheeltug) extra weight, over the useful life of your aircraft, then add maintenance, I don't see the advantage. I guess I'm saying tugs don't fly, A/C don't tug. Offering an expensive perk to the ground authority without payment, is not good business. If you're flying into tugless strips, be happy with your propellors, not your Jet sucking hot pipes. I think you'll like Hotel. Keep going, all the best.

Airfoil

[keesje]

Would your design be better than this for comfort? If not, passengers will eventually shun it.


Hi Pettifogger, I've flown several times on F27 variants and F28. Both are very loud indeed on the outside and on the inside. Deafening. http://www.youtube.com/watch?v=Vycf4odW1_Y&feature=related (http://www.youtube.com/watch?v=Vycf4odW1_Y&feature=related) A proud dutch product but developped 50 yrs ago.

The new engine / prop I proposed is the TP400. It is developed to turn slower and avoid the typical tip effects and has better turbine noise isolation.. http://www.youtube.com/watch?v=h-V5jzSslZo (http://www.youtube.com/watch?v=h-V5jzSslZo) It will allow the A400M to use civil airways flying M0.7 at up to 37.000 ft.

Apart from that it seems passenger comfort is really moving down the priority list as airlines struggle to survive the constantly rising fuel prices. http://www.iht.com/articles/2008/03/24/business/turbo.php (http://www.iht.com/articles/2008/03/24/business/turbo.php)

As said earlier, the shorter the trip, the better the turboprops look. I summarized a selection of city pairs in Europe. More then 700 million people live in Europe, but the more wealthy ones live in the western part, all very close together. As can be seen most major city pairs are closer then 400nm. Very high frequency flights are flown, often even by twin aisles.. Then there are flogs of 737 / 320 aircraft doing low cost flights within the same area. The big hubs are seriously restricted. A different situation then e.g. the US or Asia..

http://i191.photobucket.com/albums/z160/keesje_pics/Europecitypairs.jpg?t=1210977129

I think you'd need means to assist evacuation from the emergency windows (as there is no wing there). Given this, I think a smaller door (739 style) will be better to be put where the emergency exit windows are, or maybe move it clear off the sponsons... as you need a slide from the exit and you don't want it to get poked by the wheelbay door or landing gear mechanism.
PK-KAR good point. The doors won't very very high, but high enough to have some kind of slope. I moved them and made them bigger.


I was wondering if someone would do a mini Tu114 twin


It didn't happen. Antonov studied a 720 seat prop version of the Anteus, but obviously did not build it. Luckely I guess, there would be (even more) deaf old people in Siberia.;) http://video.google.com/videoplay?docid=7136291503511317285&q=&hl=en (http://video.google.com/videoplay?docid=7136291503511317285&q=&hl=en)

I don't think that's a consistent approach; you're going to have to build in a level of hydraulic redundancy to address the roll axis, so you may as well use the same systems for the other axes too.

I'm not convinced of the need for a "high speed" aileron option, nor am I convinced that not having spioilerons is a good choice

Mad (Flt) Scientist thnx for your comments. I removed all trims to avoid unconsistancy. I think if one looks close more deatils can be found to be inconsistent. That is because it is a powerpoint concept. On the horizontal and vertikal stabelizers; both are bigger then the similar sized but heavier A320.

I see no provision for ground lift dumping, other than the slightly oddly located "direct lift spoilers". Why are they so far forward - they are going to infringe on the fuel tank volume sat in the middle of the chord. Usually they'd go just ahead of the flaps so they could mount on the rear spar.
The DLC is something different then ground spoilers. They are used inflight to decent is a very precise without changing angle.The lift distribution on a supercritical wing is spread out over the chord. Placing close to the flaps would have limited effect. Aircraft like the L1011, F14 and gliders have a DLC system. The spoilers on the Turboliner are not as big as conventional spoiler and can be fully extended when the gear is on the ground.

On the wheeltug system: most see it as a burden. I guess if you fly an aircraft priorities are reliability and performance. When buying and aircraft and negotiating with airport authorities on landing right & evening slots, rising fuel prices, environment targets, growth and noise pollution, other priorities come in. In terms of weight and reliability electric systems aren't what they used to be (ref. 787). The installation would be a few hundred lbs but save fuel.

Still I changed the design to a conventional ARJ type of gear to satisfy concerns put on the table by many (airfoilmod)

http://i191.photobucket.com/albums/z160/keesje_pics/turbolinermai17.jpg?t=1210982850

thnx for the comments! rgds keesje

[Dan Winterland]

I quite like the idea of DLC, but in practice on the L1011 - it wasn't so useful. It was designed to prent big lift changes with small attitude changes on the approach. In practice, it was awkward, added weight, difficult to maintain and was eventually disabled by a lot of L1011 operators. As for the crews, you either loved it or hated it. And when activated, it made the landings somewhat firm in a lot of instances.

Also, have you thought about the effect of positioning the spoilers in the accelerated flow behind the props? If they're used in flight, I reckon you will get quite a bit of buffeting.

[keesje]

No that you'll have convinced me electric drive maybe isn't a good idea:

Airbus could run electric taxi demonstration on A320 this year.

Airbus could undertake a demonstration of an electric taxi system on an A320 this year as part of studies to reduce fuel burn and emissions.

http://www.flightglobal.com/articles/2008/05/19/223758/airbus-could-run-electric-taxi-demonstration-on-a320-this.html

Maybe it is a good idea afterall ?

http://www.abtn.co.uk/Assets/Images/Other/wheel.jpg



I quite like the idea of DLC, but in practice on the L1011 - it wasn't so useful. It was designed to prent big lift changes with small attitude changes on the approach. In practice, it was awkward, added weight, difficult to maintain and was eventually disabled by a lot of L1011 operators. As for the crews, you either loved it or hated it. And when activated, it made the landings somewhat firm in a lot of instances.

Also, have you thought about the effect of positioning the spoilers in the accelerated flow behind the props? If they're used in flight, I reckon you will get quite a bit of buffeting.

Dan, I've got to take a closer look at DLC & buffeting. As I mentioned the Turboliner is made to do high frequency short flights from busy airports.

The L1011 was developed nearly 40 years ago without 7-8 approaches a day in demanding airport environments in mind. Fly-by-wire wasn't on the capability list either. (great machine though).

I was thinking on more subtile spoiler system then the conventional big plates killing lift after touchdown. More of a very responsive automated system continuously translating pilot inputs into a combination of various controlsurface movements to achieve smooth height adjustments without gaining speed or changing pitch..

[airfoilmod]

I think you are on target with DLC. It is an effective enhancement to stability and ride. Don't get too excited about wheel motors. Keep in mind it is early on, and the French (EU) obsession with IPCC and Climate change is a bit behind the curve (not in front). If I had the space I'd offer my arguments against the concept. It doesn't make sense even if the APGW arguments do. My suggestion to all who are interested is to enhance ground movers, they are more in their realm pulling heavy A/C and could be much improved, even to the extent of meeting heavies at the High Speed exit and transporting them to Gate (Stand) with A/C engines shut down. Or for that matter, tugging them out to the penalty box for runup prior to launch.

[PETTIFOGGER]

Hi Keesje, Thanks for the u tube and other link. I am partially relieved. I can see the sense in what you propose; just flagging up passenger comfort. I look forward to the increased short sector convenience.
rgds, P

[MadDogFlyer]

Interesting discussion, some quick remarks (doesn't claim to be complete) concerning the current configuration:
Range: You have to offer more. Take a look at the history of the Mercure (http://en.wikipedia.org/wiki/Dassault_Mercure) and it's lack of range.
Weight: Your assumptions concerning the OEW are very optimistic.
Wing design: Right now not comprehensible.
Space: During the detailed design-process, it's much easier to scale something down, than adding additional things. From my point of view, there is a lack of space for everything, especially for avionics and several supply units. Possibly, parts of the main landing gear an the wing will extend into the cabin and you have to remove some seats and you have to add an extra row: Add one or two meters of length to be prepared.
Emergency Exits: The current configuration is inflexible for cabin design. And try to avoid the use of emergency slides.
"roof top windows": You have allready mentioned the problems concerning high tension. It's not impossible to install some windows, but be prepared for a lot of problems.

[airfoilmod]

Range?? This a TurboProp and targeted for Medium short Haul with cycle ratio in the 1:1 range or less. Range? Add Fuel Tanks and Switch to High Bypass Fans?? Your Kidding?

Airfoil

[MadDogFlyer]

I'm not kidding, just trying to find more customers :8.

Short Version of the argumentation:
By offering more range, the airlines could boost their cycle ratio by flying alternatly short hops and medium haul routes.

[airfoilmod]

But then all your accomplishing is carting around unnecessary Fuel. Parallel to my Wheel tug argument: Why carry around in the air that which is better suited at the Gate (or in the Truck)? If your long sector includes stops, assumed, otherwise buy n Fly 73-, then Uplift on the go. The most expensive place to store fuel (or a tug) is ONBOARD.

[keesje]

#1 Many people say the Turboliner as specified might be too big. I envision the Aircraft as a direct 737 / A320 replacement on shorter stretches <800nm4), not for long stretches. The A320 /737 are optimized for routes up to 3000nm.

Obviously offering a shrunk version of the Turboliner, would be an option. Europrop says the TP400 has growth potential so a future stretch would be possible also.

I sketched a shrink of about 150 inch / 5 seatrow / 30 seats.

http://i191.photobucket.com/albums/z160/keesje_pics/Turboliner200.jpg?t=1213606107

#2 the TP400's first flights in getting closer finally. The Herc that has been modified is doing test runs (photo flightglobal). Note the additional struts that have been added to transfer loads/moments, damp vibrations, add structural stiffness or a combination..
A part throttle setting at lower speeds / take-off seems neccessary.

http://www.flightglobal.com/blogs/flight-international/A400M%20engine%20run.jpg

http://www.flightglobal.com/blogs/flight-international/A400M%20engine%20run%20zoom.JPG

[airfoilmod]

I've followed your work and think highly of it. With respect I'd like to play Devil's advocate for a moment. Your attention to detail is impressive, and you innovate on the fly, a very admirable quality in design. Let me ask you a couple simple and sincere questions. The Hercules is approaching sixty years of age, yet is present in large numbers, relied upon by both military and civilian owners, and has a pedigree and fact sheet that remains unequalled in many ways. Would you discuss by way of affirming your approach the need for wildly complex "improvements" and "tweaks" when an airframe of the 130's record of performance stands alone? Imagine 13k horsepower per side and fans you propose on an airframe that can be configured to carry ~250 pax (or more) transcontinental? A Twin Herc? Again, this is what if? To further Frame your work, if you will.

Airfoil

[keesje]

thnx for your kind words. I agree with you the C130 has a place of its own. I think it is becoming clear to its operators that its cargo deck and load carrying capasity is reaching its limits. Airforces want to move heavier / bigger equipment than the C130J can handle.

Its 20t capasity doesn't have much competition, the A400 is significant larger, the C27 significant smaller. The Brazilians smell an opportunity and seem to step in with the C-390 that has already attracted interest.

http://sistemadearmas.sites.uol.com.br/ca/macxc3901.jpg

For passenger use I think a good militairy cargo aircraft will have a hard time becoming a good passenger aircraft. A big cross section / large cargo deck & heavy landing gear seems to contradict low drag / frontal surface. Then there is big door in the back. Structural weight & aerodynamics are probably not optimal for passenger service.

News today is that GE foresees its new heavy 8000 hp turboshaft under development for the CH53K to potentially play a role on fixed wing aircraft..

GE plots GE38 engine's future in emerging heavylift market (http://www.flightglobal.com/articles/2008/06/25/224893/ge-plots-ge38-engines-future-in-emerging-heavylift.html)

[Throttle Arms]

You mentiond the protection plates behind the props for ice. As James mentioned previously, you may also need the reinforce the skin of the fuselage to protect from ice impact.

As seen in this image: http://www.airliners.net/photo/Banco-de-Mexico/De-Havilland-Canada/1364184/M/ (http://www.airliners.net/photo/Banco-de-Mexico/De-Havilland-Canada/1364184/M/)

[Machaca]

keesje

Your design idea has a fuselage diameter & length and wingspan almost identical to an A320 -- but its empty weight is 35% lower!

Where will your design save the 15 tonnes? Seems particularly difficult since the T-tail and high-wing/low-gear arrangements are heavier.

CFM56's weigh about 2400kg each, TP400's about 1900kg each, so there's a ton of savings per airframe. 14 to go!

[keesje]

Hi Machada,

the Turboliner and A320 share the same seat capasity, but that's about all.

Thw A320 is a heavy aircraft for short haul passenger service.

The MTOW of the Turboliner is much lower because it is not a medium haul aircraft like the A320.

The Turboliner would have significantly less then half the range / fuel capasity. (1500nm vs 3200 nm)

No serious cargo capability is foresee, contrary to A320 which has containers/pallet capability and loading system.

Turboliner wings, tail section and floor should be CRFP like all modern designs but unlike the A320.

The fuselage cross section would be narrower then A320, 3.7 m vs 3.95 m. Turboliner fuselage & cabin are closer to the BA146.

The service ceiling of the Turboliner would be around 25.000ft vs 40.000ft and max speed are lower influencing the pressure cabin / structure weight.

Lighter galleys (no ovens) just small meals, less lavatories etc, no IFE, etc.

Basicly everything is lighter because its a dedicated passenger short range turboprop without the medium haul flexibility (& MTOW) the A320 and 737 offer.

[kiwilad]

I would like to think that ovens and IFE would be in the offering as the market takes a turn downwards, the airlines are looking toward better product offerings rather than just cheap seats. they are still offering cheap seats but are now looking at adding IFE etc to ensure that what market share is available they get the maximum out of it.
Air NZ is just re-fitting the A320 & B767 fleets with IFE in the seat backs. I was surprised that they ordered the A320 without it?!?
As this technology gets lighter and lighter it maybe able to be used with out a major weight penalty.

The Atr 72 MTOW is 22800kgs that we fly and the Q400 is closer to 29t, for a difference of about 6-10seats.

Will be interesting to finally see what ATR offers as a 90seat turbo-prop concept. Also hear that Embraer are talking/planning a 90seat turbo-prop as well. So I would guess that the current fuel price issues may be the start of a very strong push toward turbo-prop flying.

Soon our fleet will be getting upgraded/replaced and the contenders were the ATR600, Q400 and ERJ190. The 600 and 400 were most likely with a view to the 90seat products ATR and DASH are looking at building, one a stretch of a old technology the other off a clean sheet with all new technology available.

My money would be on keeping the ATR!!

But wouldn't mind if they bought your turbo-prop keesje:ok:

[keesje]

Soon our fleet will be getting upgraded/replaced and the contenders were the ATR600, Q400 and ERJ190. The 600 and 400 were most likely with a view to the 90seat products ATR and DASH are looking at building, one a stretch of a old technology the other off a clean sheet with all new technology available.


It would seem Bombardier could use the new CSeries 5 abreast fuselage and many systems as a starting point. They did the same with the Q and CRJ series. C110 fuselage / cabin:

http://www.bombardier.com/en/3_0/3_8/img/C110_LOPAs.gif

A new wing & tail would be neccesary (althoung Embraer plans to use the E190's wing for the above mentioned high winged C-390)

Also good news from the engines front new heavy turbo shafts : GE38-1B (7500 hp), Honeywell a new T55 version : 55-L-71X (>5000 hp) and Rolls keeps improving the AE2100 (max 5000 hp).

GE plots GE38 engine's future in emerging heavylift market (http://www.flightglobal.com/articles/2008/06/25/224893/ge-plots-ge38-engines-future-in-emerging-heavylift.html)

[Mad (Flt) Scientist]

It would seem Bombardier could use the new CSeries 5 abreast fuselage and many systems as a starting point. They did the same with the Q and CRJ series.

I'm not too sure what you are getting at here, but there's no real design commonality between the dash 8 and CRJ fuselages. The dash started development long before Bombardier/Canadair had any involvement in Downview, and the CRJ fuselage of course is a direct development of the Challenger. So there's no common ancestor to the designs.

[Machaca]

Keesje - I'm unclear on your response to my question regarding weight:

the Turboliner and A320 share the same seat capasity, but that's about all. They share the same physics and math too.

Thw A320 is a heavy aircraft for short haul passenger service.Yes, I agree the A320 is a bit heavy for max efficiency short-haul pax service. So how do you carry the same # of pax with 14 tonnes less airplane?

The MTOW of the Turboliner is much lower because it is not a medium haul aircraft like the A320.Certainly. However, I asked about OEW.

The Turboliner would have significantly less then half the range / fuel capasity. (1500nm vs 3200 nm)This is mostly determined by wing volume available for the fuel tanks and powerplant fuel burn.

No serious cargo capability is foresee, contrary to A320 which has containers/pallet capability and loading system.I don't agree with your cargo market evaluation, but for the sake of it let's dispense with the pallet/container sytems. OK, that'll save 1.5 more tonnes. 12.5 to go!

Turboliner wings, tail section and floor should be CRFP like all modern designs but unlike the A320.So what are the calculated weight savings due to use of CFRP? The A320 is already 28% composites by weight, including the entire tail structure. The A380 saved almost 15 tonnes by the use of composites, including a CFRP wing center wing box and entire tail structure - that shaved its OEW by 5% to 277 tonnes!

The fuselage cross section would be narrower then A320, 3.7 m vs 3.95 m. Turboliner fuselage & cabin are closer to the BA146.Why? Your OEW kg per seat is lower than a Cessna 172!Some rough numbers for comparison (single class, ~31" SP):
A320-200 = 243 kg/seat
B737-500 = 242 kg/seat
Emb 195 = 230 kg/seat
BAe-146 = 225 kg/seat
DHC Q400 = 224 kg/seat
ATR-72 = 191 kg/seat
Cessna 172 = 162 kg/seat
Turboliner = 161 kg/seatThe service ceiling of the Turboliner would be around 25.000ft vs 40.000ft and max speed are lower influencing the pressure cabin / structure weight.How much weight does this shed and from where - fuselage skin thickness?

Lighter galleys (no ovens) just small meals, less lavatories etc, no IFE, etc.Basicly everything is lighter because its a dedicated passenger short range turboprop without the medium haul flexibility (& MTOW) the A320 and 737 offer.OK, galleys just like a Q400 & ATR-72 (can't cut the lavs or pax will spend entire flight in the queue!). So how does the Turboliner get to be so much lighter?

I really like the idea of a 150 seat twin TP-400 powered airliner, but more hard numbers are needed to assess its feasibility.

[keesje]

Thanks for the good look you took at the number


I really like the idea of a 150 seat twin TP-400 powered airliner, but more hard numbers are needed to assess its feasibility.


I don't think we have to go to deep for that one.

I took some data from a nice MIT study of the various relevant efficiencies influencing overall efficiency for different aircraft & propulsion types.

Report by Raffi Babikian, Stephen P. Lukachko and Ian A. Waitz can be found at: http://web.mit.edu/aeroastro/people/waitz/publications/Babikian.pdf, 2003?

http://i191.photobucket.com/albums/z160/keesje_pics/TSFCMIT.jpg?t=1214911705

As can be seen in the graph Turboprop engines tend to be 15-20% more fuel efficient then turbofans. main driver of this is the very high BPR of over 1:30. The engines used on 737 and A320 (CFM56 / V2500) are improved versions of 20-30 year old designs, the limited BPR is only 1:5. The TP400 with the latest technology build into a blank paper design is probably closer or even over 20%. SFC probably around around .4

As you mentioned Turboprops are also structurally more efficient then jet aircraft. This has to do with their limited flight envelope and dedicated short haul passenger design.

http://i191.photobucket.com/albums/z160/keesje_pics/mitstructefficiency.jpg?t=1214911991

This structural efficiency results in lower weights and lift induced drag. Taxiing efficiency is also much better for high frequency operations. Other efficiencies are of a lower order. These considerations made me conclude a 25 % more fuel efficient operation should be possible with the Propliner compared to e.g. a similar sized 737 or A320.

Question arises why it hasn't been tried earlier. I think fuel was a smaller part of total operating costs. Increased speed (=frequencies) and medium range flexibility were more important. Nobody felt the need to develop a higher BPR engine like open rotor or real big turboprop.

[Machaca]

Keesje
Quote:
I really like the idea of a 150 seat twin TP-400 powered airliner, but more hard numbers are needed to assess its feasibility.I don't think we have to go to deep for that one.How about wading into the shallow part and providing some basic answers? How will you shed the weight? This is the Tech forum, not the brochure-speak dream forum.

I took some data from a nice MIT study of the various relevant efficiencies influencing overall efficiency for different aircraft & propulsion types.No you didn't. You extrapolated wildly from a graph to guesstimate a desired outcome.

...Turboprop engines tend to be 15-20% more fuel efficient then turbofans. main driver of this is the very high BPR of over 1:30. The engines used on 737 and A320 (CFM56 / V2500) are improved versions of 20-30 year old designs, the limited BPR is only 1:5.The graph represents aircraft, not engines. I asked about airframe weight, not BPR.

The TP400 with the latest technology build into a blank paper design is probably closer or even over 20%. SFC probably around around .4How did you derive such a claim?

As you mentioned Turboprops are also structurally more efficient then jet aircraft. This has to do with their limited flight envelope and dedicated short haul passenger design.I mentioned no such thing. Short haul aircraft are structurally reinforced to handle their high cycle operating environment. This adds weight.

The MIT study you linked to contradicts your statement:"...RJ's are less structurally efficient than large aircraft, and that TP's in turn are less efficient than RJ's."
These considerations made me conclude a 25 % more fuel efficient operation should be possible with the Propliner compared to e.g. a similar sized 737 or A320.Time to reconsider what conclusions are possible!

Keesje, there are many highly experienced and knowledgeable aviation professionals willing to contribute meaningfully to your idea if you are willing to engage in a honest dialogue.

[keesje]

"How about wading into the shallow part and providing some basic answers? How will you shed the weight? This is the Tech forum, not the brochure-speak dream forum."

"No you didn't. You extrapolated wildly from a graph to guesstimate a desired outcome."

"The graph represents aircraft, not engines. I asked about airframe weight, not BPR."

"How did you derive such a claim?"

"I mentioned no such thing. Short haul aircraft are structurally reinforced to handle their high cycle operating environment. This adds weight."

"The MIT study you linked to contradicts your statement:

Time to reconsider what conclusions are possible! "

"Keesje, there are many highly experienced and knowledgeable aviation professionals willing to contribute meaningfully to your idea if you are willing to engage in a honest dialogue. "


Machaca, excuse if I angered you, if I appeared dishonest> I did not intend to avoid basic answers!

As I mentioned in earlier posts (#6) I did not take the B737 or A320 as a starting point. I took the BAE146 family (fuselage) and TP400 engine (MTOW) as starting points. As you can see in the first post the Turboliner shares the tail, landing gear and general wing configuration. If we look at the last biggest ever BAE146 variant, the RXJ100, it has an empty weight of about 25.450kg (56,108lb). The max 120 seat Fokker 100 is a tonne lighter.

http://cdn-www.airliners.net/aviation-photos/middle/3/7/0/0240073.jpg
This photo no doubt creates sad feeling for UK readers.. sorry, the only RJX100. Specs: http://www.airliners.net/aircraft-data/stats.main?id=48 (http://www.airliners.net/aircraft-data/stats.main?id=48)

The RJX has a 1500 kg lower OEW then the Turboliner. The RJX basic airframe & wing were developed about 35 years ago.

Taking the RXJ1000 & TP400 as a starting point (as I did: http://i191.photobucket.com/albums/z160/keesje_pics/tURBOLINERBIRTH.jpg?t=1214997582 ).

Replacing the 4 engined BAE 146 wing with a new CRFP wing with 2 engines will save weight. : 1500 kg?
Replacing the the RXJ's Al tail with a CRFP one will save weight 1000 kg?
Replacing floor and floor beams and torsionbox with CRFP : 1000 kg?
The Turboliner has less range, max speed, lower ceiling : xxx kg?That leaves ~5000kg for the 6 meters fuselage stretch (2 plugs) and seats / cabin and other adjustments that come with it. Not an unreasonable estimation I think.

Maybe I'm optimistic and the OEW is higher. An OEW close to the A320 as you suggest would be to high IMO. I don't think its like comparing a SUV to a compact car, but the designs have different missions for sure. ;)

kind regards,
keesje

[keesje]

Rolls-Royce is talking up the possibility of a new generation of turboprop-powered aircraft replacing a substantial proportion of today's narrowbody jets.
The manufacturer believes high oil prices are likely to drive airframers to sacrifice cruise speed for economics.
"The TP400 engine [for the Airbus A400M military transport] is a very efficient propulsion system," R-R director engineering and technology, Colin Smith, says. "There is a very sound argument to be made for the majority of the 150-seat market, which flies mostly for less than 1.5h [being turboprop-powered]...if somebody does want a high-efficiency turboprop then have we got one for you."



"All we know is that a lot of people who currently fly around in 150-seat aircraft will need transporting in the future. Is that going to be in a single-aisle or twin-aisle? There are plenty of persuasive arguments about what that will be.
"What is the range of this thing? A thousand miles [1,600km] or 3,000 miles leads to fundamentally different machines."


Rolls-Royce promotes turboprop solution for new civil airliners (http://www.flightglobal.com/articles/2008/07/01/224987/rolls-royce-promotes-turboprop-solution-for-new-civil.html)

:ok:

[Dan Winterland]

And I bet they've been looking at your thread, or are you connected with them?

But this is the engine manufacturer looking at the possibility of increasing the market for it's product. They do mention that they haven't spoke to the airframe producers yet. I suspect those companies have some drawings for aircraft similar to yours. But I suspect the reason they haven't come to light is that it's just not yet viable. With oil heading for $200, it may just yet.

The A320/B737 designs have evolved from a design concept which fits the current market requirements. Your high capacity TP design looks like it is trying to justify it's design by stealing the business from the current designs. But it's going to have to fill a niche, and I don't think the market is quite ready to change just yet. But who knows what the air travel market will be like in 10 years time.




Just one point about the reduced size cargo holds. A lot of routes need freight business to stay profitable. I fly A320s around China and we nearly always have at least 2 tonnes of freight in the holds.

[Torquelink]

Interesting thought - when does a turboprop become an open rotor / unducted fan and vice versa?

[keesje]

are you connected with them?

No, I've never had anything to do with RR.


Just one point about the reduced size cargo holds. A lot of routes need freight business to stay profitable. I fly A320s around China and we nearly always have at least 2 tonnes of freight in the holds.


I think the strenght of the A320 is that it is able to load cargo containers and a full passenger load and fly it over medium distances like in the Chinese market. But it is also the reason that it is relatively heavy / overpowered for short trips. On short trips cargo is less important. Door to door trucks / didicated transport chains in populated areas are hard to beat for the shorters sectors the Turboliner would serve.

I tried to dimension the cargohold to be just big enough to handle the luggage for a full load of holiday travellers. Lowering the floor created room for big luggage bins enabling more hand luggage for short haul / day business trips to e.g. LCY.


Your high capacity TP design looks like it is trying to justify it's design by stealing the business from the current designs.


No that's not the intent. The intent is to provide a feasible low risk way to reduce fuel costs by at least 20% in the important 150 segment. Airlines are begging for that. :{

Airbus and Boeing have enormous backlogs and are in no hurry, saying breakthroughs are neccessary that can not be done before 2020. :hmm:

[Dan Winterland]

Quote: I tried to dimension the cargohold to be just big enough to handle the luggage for a full load of holiday travellers. Lowering the floor created room for big luggage bins enabling more hand luggage for short haul / day business trips to e.g. LCY.

Then the design is going to be restricted in it's use. You are consigning it to a limited market. I don't think it would fit in the Asian market, which is the biggest emerging market at the moment and can't be ignored by any manufacturer.

[keesje]

Then the design is going to be restricted in it's use. You are consigning it to a limited market.
Yes, that's basicly the trick. One aircraft that can do it all is an inherent compromise. On shorter distances (e.g Europe) you pay a high price for this flexibility. With fuel prices approaching 35% of total airline costs it is becoming no longer acceptable for the operators.

The NB market is so big dedicated types for various markets will probably be a smarter solution. So no 1-1 replacement, but a split. In the narrowbody market we allready see the Superjet, CSeries, Embraer 190/195, ARJ pushing out the heavy 737-600-700 and A318/319 where the payload range capasity of those types is not needed.

http://gc.kls2.com/cgi-bin/gcmap?RANGE=1200nm%40PVG,1200nm%40MIA,1200nm%40JFK,1200nm%40 DXB,1200nm%40AMS&MAP-STYLE=azeqi&MAP-CENTER=FRA&RANGE-STYLE=best&RANGE-COLOR=navy

1200 NM ranges from MIA, JFK, AMS, DXB and PVG.

Luckely people live together in populated areas. Even in China most traffic is concentrated around the East Coast. Ghuanzou is little more then 1000nm away from PEK. Inbetween most activity seems concentrated. A320/737s could take care of longer / cargo included flights.

[MadDogFlyer]

Yes, that's basicly the trick.Sorry, but thats becomes more and more the basic problem.


Even with a perfect aircraft, short flights are bad for business. On the one hand, there are a lot of other means of transport, on the other hand, a lot of costs of a flight accumulate per flight/per cycle and not per flight hour (e.g. landing fees, maintenance costs). The limit of 1500NM is leaving only a small spectrum of ranges, where airlines earn money. Take a look at the BAe146 and the lack of range and the lack of success of this aircraft.


A smaller and very light airframe could be the first step to a more fuel efficient aircraft. But while the whole aviation world is talking about the fuel price, airlines are paying leasing rates (or interests), spendig a lot of money for maintenance, paying fees and give money to the crew.

Saving 500kg fuel from LHR to AMS woud be great, but if the other costs are to high, you can't sell even one Turboliner.

Again, here arrives the weight at the scene. You want to offer a short range aircraft, which is flying thousands of cycles (round about 100.000 cycles in 30 years ?!). And the weight is lower than anything known today. This could work, but the mechanicians would have to change a lot of structural parts during the life cycle. In this case, the maintenance costs would hit the roof.

Take the average structure weight of some comparable modern aircrafts (320/737) and subtract 10%. This would be more serious than scaling up from a very special kind of aircraft like the BAe146.

[keesje]

Saving 500kg fuel from LHR to AMS woud be great, but if the other costs are to high, you can't sell even one Turboliner.

Of course saving any 500 kg would be great, however that's not the situation on short haul >120 seat operations at this moment.

A ~120 seat Boeing 737-600 weighs empty : 80,031 lb (36,378 kg), A318 more.
A ~110 seat Fokker 100 weighs empty : 53,510 lb (24,272 kg)

Difference in OEW is 30% or 12.000 kg. That's the same as the payload weight of the 120 passengers + their luggage.


The limit of 1500NM is leaving only a small spectrum of ranges, where airlines earn money.


1500NM easily covers the 700 million Europeans and 800 millions Chinese living on the East coast and more then a billion people from Delhi.

Take the average structure weight of some comparable modern aircrafts (320/737) and subtract 10%. This would be more serious than scaling up from a very special kind of aircraft like the BAe146.

IMO Aircraft made for short haul operations are all significantly lighter then 737/A320. Thing is aircraft like the BAE146, F100, 737-100, DC9 and BAC One-Eleven where never replaced. Bigger aircraft offered more payload / range flexibility & fuel prices weren't a real issue (in the sense that it killed airlines).

I have the feeling Bombardier with its lighter dedicated more fuel efficient 110-130 seater will have a ball next week and in the coming years.. ATR is looking at stepping in too with a 100 seat prop. ATR refers to new turboprop study as '-900' (http://www.flightglobal.com/articles/2008/07/09/225165/atr-refers-to-new-turboprop-study-as-900.html). At this moment Embraer is king of the hill. Airlines simply had no alternative during the last 10 years.

http://www.skycontrol.net/UserFiles/Image/BusinessGA_img/200609/200608-EMB195_Flybe-08_alta.jpg

Again, here arrives the weight at the scene. You want to offer a short range aircraft, which is flying thousands of cycles (round about 100.000 cycles in 30 years ?!). And the weight is lower than anything known today. This could work, but the mechanicians would have to change a lot of structural parts during the life cycle. In this case, the maintenance costs would hit the roof.

True. Knowing in advance the aircraft will be used shorthaul, high frequency would be a design requirement. On the other hand giving in at range, payload, ceiling and speed would make everything lighter, aslo the structural loads. Adding metal in the places where it should be is a matter of good design, as well as e.g. good accessibility for inspection & repair.

[Lordarpad]

hiya

I see madog's point but I also think that at this stage it would be interesting to know why the F100 is so much lighter than the B737-600.

On balance I think you are on to a goos thing keesje, but I am going to throw a few spanners.

My most basic question is why you are using such a conventional layout when there is a layout that rather clearly is a very good fuel saver and is happily competing with jets in it's field: the Piaggio Avanti II.

Details for the config are here: Showcase (http://www.piaggioaero.com/en/products/aircraft/p180/showcase/showcase.php)

25% better than a normal turboprop sounds too good to miss if you are planning to compete on fuel cost. Scaling could get interesting, but the Avanti is not that unknown an aircraft anymore. And I am sure Piaggio could be persuaded to a joint venture.

The other problem I have is that as a passenger I have a severe dislike of the BAe 146 in 6 abreast layout. I once sat in a row with 2 other big guys and we actually had to tile our shoulder in order to fit! I consider 737-width to be the bar minimum. What I am wondering is why you are not using an ovoid fuselage such as the A350 in order to make more space?

On a very basic level I'd also say that the income from freight is so significant that that rather makes the space for it worthwhile.

Other points from this discussion:

- I would support a ceiling of at least FL320 or so to be able to avoid the weather.

- Speed: 380 kts or so I am thinking. For the jet proponents:

SAS are already flying slower with their jets in order to save fuel:

SAS flies slower to save costs and emissions | Environment | Reuters (http://www.reuters.com/article/environmentNews/idUSL2076257020080520)

So I would not think that that is any kind of criterium for these kind of flights.

Overall I love this idea and am looking forward to the further development of this. I have also seen the posts on airliners.net

cheers

Bernhard

[datafuser]

What's the noise target of the Turboliner? In the 1990's Saab promised 76dB to Crossair but achieved only 78 dB, much to Crossair's annoyance.

Sunho

[keesje]

What's the noise target of the Turboliner? In the 1990's Saab promised 76dB to Crossair but achieved only 78 dB, much to Crossair's annoyance.

I think good progress has been made in this area. The level, frequency & characteristics combined with new fluid dynamics technology has provided significant improvements.. e.g. the sharp wingtip transsonic noise seems almost eliminated.

YouTube - Airbus A400M TP400-D6 Engine Test (http://www.youtube.com/watch?v=h-V5jzSslZo)

They should do some wotk on the starters though (or go for electric drive & start at a more remote place)..

YouTube - Fokker F27 Startup and Taxi (http://www.youtube.com/watch?v=Vycf4odW1_Y)

[straccaletto]

Ciao to all,
is there any evolution of the idea two years later?
Thanks
Francesco

[Big Pistons Forever]

If you really want efficency bring back props and a big piston engine to drive them :ok:

[bearfoil]

keesje

You have a facility for design, and you think well. I liked your work the first time around, should you be on to other projects? The Big propellor Turbojet marriage has some pretty efficient expressions in millions of hours of Turbofans. So my suggestion is take your refreshing airframe approaches to the Turbofan solution. Propellors are heavy, complex, way expensive given their "advantages", etc. Nice work! Altitude constraints limit the Propellor to high drag environment, and Propellor speed limit by Noise at low level.

bear

[PeetPeet]

Just happened upon this thread - very interesting, only suggestion I would make is enlarging the rudder relative to the vertical fin, area ratio looks wrong. Hydraulically powered FBW controls would seem to be the modern approach to the flight controls, mechanically linked hydraulics is cheaper to develop, more expensive to maintain later.

[keesje]

Thnx Bearfoil. Nothing official came out of this concept. Btw since a few months I'm looking for a job after reorganization at my employer. With my "partner in crime" kaktusdigital (Henry) I'm working on an update of the Turboliner. He's a graphics professional, stay tuned :cool:

[SMT Member]

Keesje,

If you're working on an update, may I suggest you start looking at a freighter? The basic dimensions of the floor would probably accomodate a standard 125 inch (318 cm) by 88 inch (213 cm) ULD. Try to make sure you can have around 220 cm of height clearance over a width of around 100 cm at the roof. That will allow loading of standard AAA type ULDs. Also, ensure there's room for a restraining system by placing the ULDs with around 1 inch of space between each position.

Cargo door should be behind the wing, wih dimensions of around 220 cm high by 340 cm wide.

If you can make all that happen, and add a couple hundred miles more range, you'll have a feeder par excellence for the integrators on your hands.

[PaulW]

Maybe because I fly it, and its a no longer produced low production run aircraft, through being a victim of circumstance I have noticed no one has mentioned the Saab 2000. Its not mentioned on any of the graphs shown of current aircraft comparisons.
I like the proposal but my primary concern is service ceiling Fl250 is far too low. Whats the point of a 1500nm range if you gonna be limited to Fl250.
Maybe chemical oxygen generators or a ring main oxygen sytem adds weight but the fuel savings would be astronomical. Take the performance of the A400m even if you wont plan to be doing long sectors to always require FL370, the performance would be there with regard to payload and shortfield operation and high ceiling when long sectors are flown. I would also opt for low wing wide landing gear for crosswind ability and minimum control speeds. The Saab 2000 has a Fl310 service ceiling and you can choose to take RVSM or non RVSM packages for avionics and maintenance solutions. Saab claim that paying the extra for the RVSM ADCs and package will pay for itself in 6-9 months on an aircraft doing 8 400nm sectors a day. Operating at 300 and 310 instead of 270 and 280.
When appropriate even though the airframes my company operate arent RVSM approved we often ask negative rvsm for higher, and in quiet airspace with a friendly controller are approved. The Saab gets to 310 with plenty of spare performance, its the differential pressure limitation on the fueselage that limits the SB20.
The Saab 2000 is worth a study as although it was not a success due to bad timing in the market and some interesting decisions from the manufacturer regarding the production jigs when production ceased is a much more advanced turbo prop than what is currently available even 15 years later in the civil market. Due to the Saab being late into production, for whatever reasons large orders were cancelled, and in a rush to bring into production some compromises were made, but when operating the aircraft you can see what awesome potential it has, and would have had if ideas had been taken to the full.
A wide bodied (capable of taking 3+3 seats or a ULD or AKE at least for a cargo version) stretched version of the Saab 2000 would be my choice with full fly by wire rather than just pitch and yaw, an improved pressurisation/environmental control system and autothrottle/full VNAV with proline 21 instead of proline 4, and 440kt TAS FL370 ceiling would be my perfect aircraft. Also take a look at the Piaggio Avanti for Turboprop performance.
I understand this is an old thread that has been resurrected but I will add my best wishes for your project. What is the status of the project now?

[keesje]

SMT Member, thnx

the revised concept we are working on, has a wider flatter cross section, an innovative 2-3-2 standing cabin, around (9x20") 180 inch (4.5) wide at seat level. The cargo possibilities crossed my mind, thanks for the more detailed requirements. I think even 2 LD-3s might fit side by side.

http://freightpad.com/images/2010/04/LD-3.gif

220 cm of height clearance over a width of around 100 cm at the roof should not be a limitation. Even some bigger pallets might fit in if the door is wide enough to make the turn.

PaulW I got more comments on the performance. thnx for your input. The new concept will have state of the art counter rotating open rotors optimized for better performance and Henry smoothened out aerodynamics. I'll have to study the effect on the specification in terms of OEW etc. The aircraft will remain high wing but we widened the landing gear for said crosswind ability and minimum control speeds. The high wing and two passenger doors will enable quick (de) boarding on smaller airports and enhance airfield performance for a given span/surface.

The status is that we started looking at it again before the (euro) holidays and now spend some time on it again & think about how to best present it apart from pprune and airliners.net. The concept graphics Henry produced so far look very good. W'll add some more detail. All suggestions / ideas are welcome.

kind regards