@FDEdev where are the horrible performance numbers ?

@FDEdev are you going to expand regarding the ''issues'' you find or not

Your aircraft is roughly the size of a 767, but weighs approximately the same as an A321.  

Your engines have more thrust than a 190t 767, but your plane weighs 100t less.

Despite these super-engines, the cruising speed and even the max cruising speed are way too low to be acceptable/usable.

The same goes for the ceiling.

An A321XLR has the same range as your design, but requires 77000l less fuel.

Just to mention a few points.

Over and out.

 

 

 

I don't wish to sound mean, but I would perhaps highlight some other stuff too which is more than a little problematic with the design...

The fact that it has a very low cruise speed and a particularly low service ceiling - which is a very bad combination for an airliner and even more so for a luxury one - means it would be problematic for ATC to route this thing into busy airspace. It would be in the way of everything else all the time, i.e. the B737 and the A321 (the two most numerous airliners in the world), can both cruise at a much higher speed than it and much higher altitude too, so they would either be constantly having to avoid it on climbs and descents, or if unfortunate enough to be slotted in behind it at a similar cruise altitude, or more probably, your aircraft would have to be sent on a more circuitous route so it wasn't in the way of everything else.

A big problem in relation to that scenario, is that with a low service ceiling, it would also have to fly even more circuitously to avoid weather, since it would be unable to climb above thunderstorms, turbulence and icing conditions. Given that you have suggested that it is a luxury aircraft, configured for 50 first class passengers, you would be expecting people who have paid top-dollar for their tickets, to travel really slowly via an unnecessarily long route (severely limiting its practical range) and quite probably uncomfortably too since its ability to find clear air seems extremely limited in terms of flight level options.

By way of comparison with a genuine luxury aircraft, note that the Gulfstream G650 can carry 20 passengers in luxury, at Mach 0.9 and at an altitude of over 50,000 feet. So, ask yourself this: If seat ticket price was not a problem, would you choose to fly on something which could get you there at just shy of Mach 1 on a pretty much direct route since it can fly above all the regular commercial traffic, or something which will be ponderously wandering all over the place at Mach 0.7, constantly being given vectors by ATC to get it out of the way of speedier traffic and weather systems which would destroy it, and which as a result, would frequently not even be able to depart in severe IFR conditions because of its inability to avoid that weather.

Beyond this, it doesn't look a particularly feasible design in terms of structural integrity either. There appears to be very little in the way of a main wing box at the fuselage, but more importantly, the long thin spindly wings which feature some (as far as I can surmise) largely pointless gull wing cranking going on, would make for a weak main spar. This does not exactly inspire engineering confidence in your design. Major airliner designs have in the past had problems with making modern composite materials, which they want to use for reasons of lightness, strong enough to withstand the flexing a wing undergoes, two reasonably recent examples being the MD-11 and the B787, both of which experienced cracking of the wing spars on their initial designs, requiring considerable strengthening to be implemented for the final design. This is in fact why the 787's wing is a long sweeping curve, rather than one which features any abrupt changes in angle.

All credit to you for having a go at designing an aeroplane, and I would not wish to put you off continuing to do so, but it's not as easy as it might appear to knock something up which is genuinely practical. But if you want some pointers on that for your next stab at it, what airlines are looking for these days, is aeroplanes with good range, rather than massive capacity, so something about the size and performance of a 737-700, but with considerably greater range, would be an aeroplane most airlines would be very interested in.

A good start for any airliner design, is to look at the cargo requirements for a specific type and the size of ULD containers and their weight limits, then design your aeroplane around that information. This is how most airliner designs start out. So for something like your aeroplane design, you would probably want it to be able to carry AKH ULDs, which would determine its cabin width and its length for the consideration of the take off rotation angle given the placement of the engines and their power rating, but you also need to consider things such as the exact engine placement for practical issues such as controllability at take off and landing speeds should one of those engines fail, which then determines the height and placement of the vertical fin and the size of the rudder as well as the wing area, sweep angle and the control surfaces on that wing.

Good luck with it.

 

Edited March 19, 20206 yr by Chock

@FDEdev @Chock

Thank you for your indications, I will revise and work in all aspects you mention. Upgrades in the near future will be clarified.

@Chock lots of info and really interesting, I will work on it.

 

 

 

 

 

 

 

Edited April 29, 20206 yr by mp15

What do your think of the specs update?

I can't really comment on the specs update as I'm not an aircraft engineer. I used to be an aerospace weight engineer, but that was many years ago....

She looks like a cross between a business jet at the front, and a 757 for the rest of here apart from that different, almost crescent shaped wing, reminiscent of the Handley Page Victor's wing. She's different, but not unattractive..

The wheels look quite sporty from the picture. Almost what your find on a modern sports car. Wouldn't aircraft tyres have to have a larger sidewall to help cushion the landing forces? I know some fighter jets had incredibly high tyre pressures on narrow wheels, but this isn't a fighter.

I'm curious about the large main undercarriage bogie. The axles seem quite a distance from each other meaning that unless you have some complex geometrical solution happening when the gear retracts then that's quite a large opening in the wing and fuselage structure...

thank your for your feedback, I am going to make the wheels sidewall less low-profile, but I'm going to keep "low cushion" permissions because of two reasons: It Is important to me to take off in a relative short distance and high profile wheels tend to be more stable but slower and the pressure settings of the wheels is slighltly more strict than regular aircraft, meaning this aircraft Is a bit less permissive on hard landings or the tires will blow up.

yes there is a complex but really simple geometrical solution for hear retraction so that i can have nice separated axles for stability 🙂

Edited April 30, 20206 yr by mp15