Future aircraft design

[thundair]

I just had a discussion with one of my colleges and was wondering if we were working on one of the last nacelle engine mounts for aircraft.
My belief is that in-body planes are more fuel efficient and will accommodate more passengers’ for the size. What are some thought along this line of thinking?


Cheers

I don't know anything but the people that do.

 

[rb1957]

the comet lost out to the B707 some decades back.

"in-body planes" = blended wing body (a la Boeing's designs for future transports) ?

 

[MikeHalloran]

Internalizing the engine(s) makes R&R more difficult, and exposes more primary structure to collateral damage from engine explosions.

Every design decision in an airplane is a compromise. The balance points of those compromises reflect external, sometimes global, pressures. Recently, fuel costs have been unstable and trending upward, while engine reliability has been steadily improving, so hiding the engines to save a bit of fuel makes sense, for now.



Mike Halloran
Pembroke Pines, FL, USA

 

[thundair]

I was thinking somewhere between Airbus' new ‘intelligent’ body and the B2
We design nacelles to survive a blade out now and Iam sure we could contain more damage if needed.
At least an in body won’t fall off ala DC10
Another advantage would be less prone to bird strikes as the in body engine does not present such a large opening to in the wind

Cheers


I don't know anything but the people that do.

 

[IRstuff]

"At least an in body won’t fall off ala DC10"

BUT, if you also recall, it was a DC10's tail engine that severed all hydraulics that caused a different crash.



TTFN
faq731-376

 

[rb1957]

the biggest question with blended wing bodies is whether the pax will like it.

airplane design is such a crap shoot. you're planning an airplane 10 years before it flies, trying to predict what the flying trends will be something like 10 years beyond that (when you've spooling up the production line). airplane design is all about compromise, and you're guessing how costs will change, how air traffic trends will change, how politics will change, and how much your government is willing to support you.

 

[thundair]

I did think of the tail engine in the DC10 when I posted the "fall off" remark.
That’s why I included the idea we could make it stronger to survive a blade out anywhere.
Although I have seen the MD11 engine and pylon (or maybe it is just called a mount) up close and personal and I don’t remember if there was blade out protection on any part of that engine.
I only have a little over a year before I retire but I will still keep an eye on trends. I guess it’s in my blood.

Cheers


I don't know anything but the people that do.

 

[WKTaylor]

High by-pass fan engines [large diameter] become very impractical to bury deep in fuselages/wings. Low by-pass fan engines have been burried successfully in many military designs. However, engine failure in a burried engine design is risky business... especially when carrying PAX or crew that cannot eject. Fratricide of an adjacent engine or critical systems is a real problem with no easy solutions. Titanium engine bays, fuel/oil/hydraulic-system armoring and isolation, system separation etc are vital elements to survivability.

Boeing designs its engine-on-a-strut to isolate the aircraft from the hell of a disintegrating engine. At best the fire/damage is contained to the strut/nacelle [at minimal weight/cost]; at worst, the engine burns-up and falls-off the wing [bad but generally never catastrophic].

Aircraft are a series of compromises: not all for efficiency.

NOTE. F-16s have no firewall surrounding the engine which saves a lot of weight/complexity. A concious decision was made decades ago, that a fire or catastrophic engine disintegration was not generally survivable, especially with a huge integral fuel tank laying over the SINGLE engine... so a highly capable and reliable ejection seat(s) were installed.

Regards, Wil Taylor

Trust - But Verify!

We believe to be true what we prefer to be true.

For those who believe, no proof is required; for those who cannot believe, no proof is possible.

 

[debodine]

I would imagine leaps are needed in sound proofing technology as well if pax are going to be seated near in body engines without complaint.

 

[KENAT]

Don't you just turn up the volume on the inflight entertainment system these days?

Else maybe active noise cancelling.

I seem to recall most images of passenger flying wings still having podded engines just their location changing.

Trident, 727 & Tristar all had one engine in the rear fuselage.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[debodine]

Ha ha Kenat, you made me grin with that one. I was thinking more along the lines of low frequency vibration that gets "into your bones" so to speak. I think hanging out on pylons may stop a lot of the LF stuff, but I not an acoustics engineer and I don't play one on TV either. (Actually, I don't play anything on TV). I am thinking a in body engine would need to be mounted on some type of vibration dampener system. It is just the ramblings of a sparky though, way out of his league.

 

[tbuelna]

.....Boeing designs its engine-on-a-strut to isolate the aircraft from the hell of a disintegrating engine. At best the fire/damage is contained to the strut/nacelle [at minimal weight/cost]; at worst, the engine burns-up and falls-off the wing [bad but generally never catastrophic]. Aircraft are a series of compromises: not all for efficiency.

Most all commercial/business turbofan aircraft use pylon-mounted engines in nacelles. And as you note there are many practical reasons for this. First, an engine attached to a pylon moves it away from the wing or empennage surface, and permits the entire nacelle to be opened up, allowing easy access to most of the outside of the engine for service. Second, mounting the engine on a pylon helps isolate the adjacent structures from damage due to fire or blade loss. Third, turbofan engines are commonly attached to the pylon using a determinate mounting system consisting of 3 "fuse pins". The fuse pins are designed to shear at a certain force. The reason for this is that the severe levels of vibration created by dynamic imbalance during an engine blade-off event can produce structural failure in the wing or empennage. Losing an engine is preferable to losing a wing.

 

[WKTaylor]

Anyone sat in the last rows of an MD80 lately? The confluence of the (2) whining engines and the smell from the toilets is enough to drive the average PAX insane on even a short 2-hour trek.

Regards, Wil Taylor

Trust - But Verify!

We believe to be true what we prefer to be true.

For those who believe, no proof is required; for those who cannot believe, no proof is possible.

 

[btrueblood]

"Anyone sat in the last rows of an MD80 lately? "

Thankfully no. Used to take the Alaska coastal flights (Seattle-California), and that was all they flew. Similar ill feelings from the rear rows in DC-10's, especially if there was turbulence that would set off that pig's dutch roll mode.

 

[Kwan]

I think Will has brought up a great design feature for the future aircraft. Mount the lavs on a pod. It will help the smell and isolate any corrosion problems!

 

[debodine]

Regarding lavatories in a pod, if someone is still unreasonably stinky, there should also be a pod eject button. I guess it would only be common decency, though, to give the pod a parachute.

 

[berkshire]

I think the Feds may have something to say on the subject.
Sec. 91.15 — Dropping objects.
No pilot in command of a civil aircraft may allow any object to be dropped from that aircraft in flight that creates a hazard to persons or property. However, this section does not prohibit the dropping of any object if reasonable precautions are taken to avoid injury or damage to persons or property.

Do you think yelling " Look out below " from 30,000 feet is sufficient warning ?
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[WKTaylor]

Watch out for blue ice falling from sky!!

Regards, Wil Taylor

Trust - But Verify!

We believe to be true what we prefer to be true.

For those who believe, no proof is required; for those who cannot believe, no proof is possible.