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by LH707330
Thu Feb 18, 2021 4:32 am
Forum: Technical/Operations
Topic: Can engines be too big?
Replies: 20
Views: 2785

Re: Can engines be too big?

What you're describing is basically the A330-100 idea: https://en.wikipedia.org/wiki/Airbus_A330#Undeveloped_variants Regarding the T500, they went up to 60k in thrust, which is similar to the highest-thrust CF6-80C2 engines on the 767, the heaviest of which is 204t at MTOW. Given takeoff drag is do...

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by LH707330
Wed Feb 17, 2021 4:12 am
Forum: Technical/Operations
Topic: Delta 757 Wing And Stabilizer Paint
Replies: 10
Views: 3338

Re: Delta 757 Wing And Stabilizer Paint

What you're referring to is called coroguard, it's an anti-corrosive coating that's made of metal flakes in a clear carrier and looks different under different light conditions. Mostly it's applied to the inspar areas where maintenance crews walk, so they want those areas to be more durable. See her...

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by LH707330
Mon Feb 15, 2021 10:44 pm
Forum: Technical/Operations
Topic: Cabin configurations, fuselage weight model
Replies: 67
Views: 5186

Re: Cabin configurations, fuselage weight model

Two possible things I can think of looking at this: 1. The seats/aisle problem shows that a tight 9Y 787 is the most efficient formula and there's not much point in going with a 7Y or 8Y for a new design under these assumptions. Assuming that Fred's checks don't reveal any serious issues with the mo...

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by LH707330
Sun Feb 14, 2021 9:30 pm
Forum: Technical/Operations
Topic: Cabin configurations, fuselage weight model
Replies: 67
Views: 5186

Re: Cabin configurations, fuselage weight model

[quote="morrisond" Yes - I believe that a 7W NMA may not be as weight efficient as a 6W - but it may not as big as a penalty as you think it may be. Remember the bare fuselage weight is somewhere around 5% of MTOW and there may be some inherent advantages of Carbon that make up some of the...

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by LH707330
Sun Feb 14, 2021 9:25 pm
Forum: Technical/Operations
Topic: Cabin configurations, fuselage weight model
Replies: 67
Views: 5186

Re: Cabin configurations, fuselage weight model

Fred, thanks for putting this together, great work! This really calls into question the design thinking behind the 767: why did they pick that diameter if they could have done a 757-300 with a bigger wing and saved weight and development cost? I suspect it may have been the case that the 767, like t...

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by LH707330
Wed Feb 03, 2021 4:57 am
Forum: Civil Aviation
Topic: Boeing CEO's Comments On Their Next Airplane
Replies: 2162
Views: 230979

Re: Boeing CEO's Comments On Their Next Airplane

Looks like Airways has that story too: Boeing Set to Produce Mid-size Aircraft | Airways Magazine. It's a bit sparse on details, claiming 270 pax at 11 hours range. That puts it at 767-300ER payload/range.

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by LH707330
Thu Jan 21, 2021 3:51 am
Forum: Technical/Operations
Topic: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!
Replies: 26
Views: 4159

Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Let's just assume that we figure out how to power planes with H2 or batteries or liquified natural unicorn farts (LCUF, it's all the range) or even fusion reactors. Why does that suddenly change the calculus around the number of fans you want (they're not "engines" unless they run by the ...

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by LH707330
Mon Jan 18, 2021 10:20 pm
Forum: Technical/Operations
Topic: What are some lesser known differences of 1st generation Boeing 777 and 2nd generation of Boeing 777?
Replies: 17
Views: 4376

Re: What are some lesser known differences of 1st generation Boeing 777 and 2nd generation of Boeing 777?

flutter wrote:
[list]
[*]The -300ER incorporates a taxi camera system which requires an extra knob in the cockpit.
.

Along with this came the racing stripes on the top edge of the wing that align with the main gear track. Airbus solved this by superimposing a stripe on the screen with the 345/346.

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by LH707330
Tue Jan 12, 2021 6:20 am
Forum: Technical/Operations
Topic: 2 vs 4 engines
Replies: 128
Views: 12642

Re: 2 vs 4 engines

I just looked it up, turns out it was the 271T MTOW that they got. Per Norris and Wagner, "changes included strengthened landing gear and attachments, a beefed-up main wing box, and reinforcement of the pickup structure for the nose and main undercarriage legs." It's unclear whether furth...

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by LH707330
Tue Jan 12, 2021 5:48 am
Forum: Technical/Operations
Topic: 2 vs 4 engines
Replies: 128
Views: 12642

Re: 2 vs 4 engines

In the sense I'm using it, similar performance means ability to perform roughly the same missions. From this perspective, MTOW is irrelevant; what actually matters in terms of how it performs as a commercial vehicle is useful load, in which the differences between the two were minimal. That said, I...

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by LH707330
Sun Jan 10, 2021 4:05 pm
Forum: Technical/Operations
Topic: 2 vs 4 engines
Replies: 128
Views: 12642

Re: 2 vs 4 engines

The A340 had about 35 tonnes higher MTOW, and significantly longer range. Original difference was even bigger. MTOW of initial versions of A330 was 212tons, 340 was maxed at 276tons. That's over 60 tons difference, almost 65. Cheers, Adam 276 only came in 1996 when Singapore pushed for it so they c...

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by LH707330
Fri Jan 08, 2021 10:59 pm
Forum: Technical/Operations
Topic: 2 vs 4 engines
Replies: 128
Views: 12642

Re: 2 vs 4 engines

The A339 now has the capability the A343 had, it is oversized for the original role the A333 had at 4000 nm, if they wanted to optimise for 4000 nm it would involve a smaller wing, and smaller engine however it would not be as effective at longer ranges, Anybody knows how much weight the new wing a...

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by LH707330
Fri Jan 08, 2021 10:49 pm
Forum: Technical/Operations
Topic: 2 vs 4 engines
Replies: 128
Views: 12642

Re: 2 vs 4 engines

Based on the above payload/range chart, the 343 and the 359 have similar payload/range near MZFW, so giving the 340 better engines would put it out ahead of the 359. At a system level it would still be less efficient though, so I doubt it would sell very well. The A359 lifts around 10 tonnes more p...

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by LH707330
Fri Jan 08, 2021 10:43 pm
Forum: Technical/Operations
Topic: VFR with Airliners
Replies: 62
Views: 5038

Re: VFR with Airliners

Yes, the question for is is just - is it worth it. What I have heard and read so far (including the great book "how and why pilots die"), from a pure safety perspective, it is a huge gap forward. From a pure practical point of view it is totally unnecessary for me. I will only fly club ma...

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by LH707330
Thu Jan 07, 2021 6:14 am
Forum: Technical/Operations
Topic: 2 vs 4 engines
Replies: 128
Views: 12642

Re: 2 vs 4 engines

Doesn't this argument also apply to the 339 with the wings being oversized for a lower fuel need? I'd imagine in the case of an A340neo, if you didn't need as much fuel, you'd leave the center tank empty and fill in more payload. Given the same structure as the 343, your range at MZFW would go out ...

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by LH707330
Wed Jan 06, 2021 7:47 pm
Forum: Technical/Operations
Topic: 2 vs 4 engines
Replies: 128
Views: 12642

Re: 2 vs 4 engines

Somewhere else I read that a slat is different and some smaller tweaks but essentially it's the same wing that was also supposed to hold the Superfan, which is basically the PW1133g. Sorry I don't see, why there needes to be a new wing. Needs to be something else. Oh guys, that would be a superb lo...

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by LH707330
Sun Jan 03, 2021 9:19 pm
Forum: Technical/Operations
Topic: A330Neo versus old B777-300ERs
Replies: 55
Views: 9140

Re: A330Neo versus old B777-300ERs

So I need to go figure out why the 787-10 sells. The A350-900 has more efficient engines. That 2.5 tons of added weight is good weight (I posted links to the EASA certification documents up thread). As someone who has designed engines, this is the tradeoff I would make. The A350-900 has a better wi...

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by LH707330
Sat Jan 02, 2021 9:44 pm
Forum: Technical/Operations
Topic: 2 vs 4 engines
Replies: 128
Views: 12642

Re: 2 vs 4 engines

Thanks for posting this, the comparisons are good to see. One claim I'm having a hard time with, however, is that fuel burn per seat for the 343 vs a 744 is 14% better. From your experience on the 343, does that number for the burn on 4000 nm make sense? It was in the order of 4-5 tonnes per hour d...

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by LH707330
Sat Jan 02, 2021 8:01 pm
Forum: Technical/Operations
Topic: BA B744 RB211 engines
Replies: 11
Views: 2149

Re: BA B744 RB211 engines

Any idea how the T versions compare on fuel burn with the GE and PW engines? I heard the initial 524G was a bit worse, curious if they closed the gap. GE and PW are in still marginal in the lead, but the gap was nearly closed with the 2% SFC improvement of the -T version. See : https://www.rolls-ro...

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by LH707330
Fri Jan 01, 2021 2:38 am
Forum: Technical/Operations
Topic: Il-86 Performance
Replies: 54
Views: 9959

Re: Il-86 Performance

Probably how to optimize detailed design elements like positioning, outboard mounts to reduce flutter, etc. and some specifics. Boeing had early issues with the twist and counterweights on the 747, and Airbus later struggled on the 340 before adding the plastron. The Russians were probably aware of...

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by LH707330
Fri Jan 01, 2021 1:47 am
Forum: Technical/Operations
Topic: BA B744 RB211 engines
Replies: 11
Views: 2149

Re: BA B744 RB211 engines

It depends what type of RR engines are installed. AFAIK BA operated a mix of RR RB211-524/H-T engines (upgraded with a Trent core) and the "normal" RB-211-524H The last 9 aircraft were factory delivered with these new engines and several more RB-211-524H's were upgraded by installation of...

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by LH707330
Tue Dec 29, 2020 5:36 pm
Forum: Technical/Operations
Topic: 2 vs 4 engines
Replies: 128
Views: 12642

Re: 2 vs 4 engines

There is a lot of misconceptions on this thread regarding the A330/A340, the bulletin below from Airbus may help educate users on how the A340 was very effective in its design mission. However the A340 design mission did not suit many operators, most operators had requirements for shorter stage len...

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by LH707330
Mon Dec 28, 2020 6:09 pm
Forum: Technical/Operations
Topic: Il-86 Performance
Replies: 54
Views: 9959

Re: Il-86 Performance

I wonder, however, what possibly could have been on the napkin drawing. I mean, all the world could "see" the underslung configuration and I have no a doubt for a second, russian/soviet aviation scientists could work out the difference in load distribution that implies on frame & wing...

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by LH707330
Mon Dec 21, 2020 1:56 am
Forum: Technical/Operations
Topic: Il-86 Performance
Replies: 54
Views: 9959

Re: Il-86 Performance

l/d Sorry, anecdotal evidence without any supporting link I find quickly. A previous life I made an intensive study project regarding propulsion efficiency and use of alternate fuels, including soviet design engines. The take from that, quite obvious for a casual observer by the severe lack of rang...

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by LH707330
Sun Dec 20, 2020 12:40 am
Forum: Technical/Operations
Topic: Il-86 Performance
Replies: 54
Views: 9959

Re: Il-86 Performance

The 96 had a completely new wing with higher span, lower sweep, and per Wikipedia, more fuel capacity as well. As far as comparisons to the A340, the Il-86 may have had slightly better T/W, but the L/D on takeoff was a lot worse, which probably made the overall performance worse as well. The Il-96-...

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by LH707330
Fri Dec 18, 2020 7:55 pm
Forum: Technical/Operations
Topic: Il-86 Performance
Replies: 54
Views: 9959

Re: Il-86 Performance

The 96 had a completely new wing with higher span, lower sweep, and per Wikipedia, more fuel capacity as well. As far as comparisons to the A340, the Il-86 may have had slightly better T/W, but the L/D on takeoff was a lot worse, which probably made the overall performance worse as well. The Il-96-3...

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by LH707330
Sat Dec 12, 2020 6:44 pm
Forum: Technical/Operations
Topic: DL & UA on Johannesburg/JNB service aircraft performance (hot & high)
Replies: 49
Views: 7516

Re: DL & UA on Johannesburg/JNB service aircraft performance (hot & high)

One metric to think about is what fraction of its MTOW can a given design lift out of JNB, i.e. JNB TOW / ISA SL MTOW. I'd be curious to see how all the designs stack up. At the end of the day, the important metric is whether your TOW is enough to lift whatever payload you want to fly profitably.

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by LH707330
Sat Dec 12, 2020 6:38 pm
Forum: Civil Aviation
Topic: large single aisle aircraft
Replies: 51
Views: 9328

Re: large single aisle aircraft

Hadn't the major carriers dumped their DC-8s and 707s within ten years or less of the entry of 747/DC-10/L-1011 into service? (When were the last orders for those placed?) Sure, fuel efficiency is important, and CO2 reduction (for some) but I struggle to imagine the passenger appeal of a 300-passen...

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by LH707330
Sat Dec 12, 2020 6:24 pm
Forum: Technical/Operations
Topic: Why does 787(and maybe A350) landing gear looks titled down instead of up during departure?
Replies: 28
Views: 4234

Re: Why does 787(and maybe A350) landing gear looks titled down instead of up during departure?

I think the 330/340 oleo is designed to depressurize so they can squeeze it in the bay. I'm not sure exactly how it works or why it was designed that way though.... They designed it that way to make it fit. ;) The oleo is not depressurised. There's a mechanical thingamabob called the "shorteni...

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by LH707330
Sat Dec 12, 2020 4:07 am
Forum: Technical/Operations
Topic: Why does 787(and maybe A350) landing gear looks titled down instead of up during departure?
Replies: 28
Views: 4234

Re: Why does 787(and maybe A350) landing gear looks titled down instead of up during departure?

I think the 330/340 oleo is designed to depressurize so they can squeeze it in the bay. I'm not sure exactly how it works or why it was designed that way though....

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by LH707330
Fri Dec 04, 2020 3:09 am
Forum: Technical/Operations
Topic: Airspeed limit under a certain altitude in China
Replies: 26
Views: 3186

Re: Airspeed limit under a certain altitude in China

Knots for airspeed. M/s for wind speed. Oh god, that's gotta be annoying to use intermixed units in the same area. At least you can approximate it as roughly 2:1 for ballparking crosswind coefficients and whatnot. As niggles go with flying in China, that's is a minor one. ;) It only really comes in...

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by LH707330
Fri Dec 04, 2020 3:02 am
Forum: Civil Aviation
Topic: 4engine MOM-aircraft reasonable?
Replies: 64
Views: 9050

Re: 4engine MOM-aircraft reasonable?

Regarding the hybrid, you thinking of Zunum Aero? Last I read, they were in trouble. The challenge with a hybrid architecture is that you have two propulsion architectures to maintain and worry about, which adds complexity. Is there enough viable space between hydrocarbon or FCV and BEVs to make it...

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by LH707330
Fri Dec 04, 2020 2:49 am
Forum: Technical/Operations
Topic: Airspeed limit under a certain altitude in China
Replies: 26
Views: 3186

Re: Airspeed limit under a certain altitude in China

Yes normally 250 below 3,000 m (9,860 ft) Ignorant question: does China use knots or m/s? Knots for airspeed. M/s for wind speed. Oh god, that's gotta be annoying to use intermixed units in the same area. At least you can approximate it as roughly 2:1 for ballparking crosswind coefficients and what...

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by LH707330
Tue Dec 01, 2020 6:00 pm
Forum: Civil Aviation
Topic: 4engine MOM-aircraft reasonable?
Replies: 64
Views: 9050

Re: 4engine MOM-aircraft reasonable?

The vast majority of NB flights are under 1500 nm, so there's no point in optimizing for a spot that doesn't get as much air time. That may start to change as electric and fuel cell gets off the ground and eats into the <500 and then <1000 mile market, forcing the hydrocarbon burners out to longer ...

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by LH707330
Tue Dec 01, 2020 5:36 pm
Forum: Technical/Operations
Topic: 777 and 787 common type rating
Replies: 26
Views: 3882

Re: 777 and 787 common type rating

I'd also be curious to see how different the systems are between A330/340 and the 757/767, which were common-type. I'd think that latter pair had more differences than the former. When you look at A330 system schematics, you can easily tell they were originally designed for a 4-engine airplane and ...

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by LH707330
Tue Dec 01, 2020 3:00 am
Forum: Technical/Operations
Topic: 777 and 787 common type rating
Replies: 26
Views: 3882

Re: 777 and 787 common type rating

Any reason the 330 and 340 are not the same type rating? They're the same plane with different engines. If I had to bet (no documents to support), I'd say it's 2 vs 4 engines. Different architecture for hydraulics, electric, resulting differences in case of abnormal procedures. Cockpit is one thing...

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by LH707330
Sun Nov 29, 2020 6:32 pm
Forum: Technical/Operations
Topic: 777 and 787 common type rating
Replies: 26
Views: 3882

Re: 777 and 787 common type rating

Any reason the 330 and 340 are not the same type rating? They're the same plane with different engines. That's a very good question. I don't know. You can do "Mixed Fleet Flying" with A330 and A340, simply alternating the checks between them. In practice, that is not much different compar...

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by LH707330
Sun Nov 29, 2020 6:25 pm
Forum: Civil Aviation
Topic: 4engine MOM-aircraft reasonable?
Replies: 64
Views: 9050

Re: 4engine MOM-aircraft reasonable?

One challenge with the NB engines is that they're optimized for shorter flights, 2ish hours IIRC. This means that they trade some efficiency for durability and maintenance. Case in point are the 320ceo engines: the CFM has a single-stage HPT to save spares costs, while the V2500 has a two-stage uni...

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by LH707330
Sat Nov 28, 2020 11:12 pm
Forum: Civil Aviation
Topic: 4engine MOM-aircraft reasonable?
Replies: 64
Views: 9050

Re: 4engine MOM-aircraft reasonable?

The economies of scale on the NB engines would definitely help you out, as would wing bending relief (see 343 vs 333), but that's about where the benefits would end. Because those engines are designed for ETOPS use, they likely have dual generators and other accessories, so you might need to remove ...

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by LH707330
Sat Nov 28, 2020 5:51 pm
Forum: Technical/Operations
Topic: 777 and 787 common type rating
Replies: 26
Views: 3882

Re: 777 and 787 common type rating

Any reason the 330 and 340 are not the same type rating? They're the same plane with different engines.

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by LH707330
Fri Nov 27, 2020 6:28 pm
Forum: Technical/Operations
Topic: Propellers/ engines on tip of wing
Replies: 19
Views: 2668

Re: Propellers/ engines on tip of wing

Electric motors are not all that heavy, so that gives you more options for placement. The reason they're put at the wingtips on designs like the Eviation Alice is to reduce tip vortices by imparting a torque on the air stream as they spin.

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by LH707330
Sun Nov 08, 2020 8:58 pm
Forum: Technical/Operations
Topic: airbus A320 wing body fairing
Replies: 8
Views: 2471

Re: airbus A320 wing body fairing

The WBF was changed at some point as well, IIRC around l/n 4***. There's a modeling thread somewhere about it, maybe on Britmodeller or Airlinercafe. Do you have an idea how I can find the modeling threads? I tried to find them but no results. Dunno, I'll try to post back here if I find them. Try a...

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by LH707330
Fri Nov 06, 2020 9:15 pm
Forum: Technical/Operations
Topic: airbus A320 wing body fairing
Replies: 8
Views: 2471

Re: airbus A320 wing body fairing

The WBF was changed at some point as well, IIRC around l/n 4***. There's a modeling thread somewhere about it, maybe on Britmodeller or Airlinercafe.

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by LH707330
Fri Nov 06, 2020 9:02 pm
Forum: Technical/Operations
Topic: Help Identify This Plane
Replies: 11
Views: 1948

Re: Help Identify This Plane

That looks a bit like a Bae 146 fuselage with CRJ700 wings and RB211-535C engines. Where'd you find it?

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by LH707330
Sun Nov 01, 2020 4:30 am
Forum: Technical/Operations
Topic: How often is the full thrust reverse used vs idle?
Replies: 24
Views: 2756

Re: How often is the full thrust reverse used vs idle?

I'd imagine you are correct in worrying about warping. Forced air cooling with fans seems pretty effective most of the time. It does make me wonder if anyone has tried to come up with a dedicated water-cooling system for brakes (either onboard or as ground equipment). I doubt it would be a good ide...

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by LH707330
Sun Nov 01, 2020 1:43 am
Forum: Technical/Operations
Topic: Some Questions About the 707 Family
Replies: 6
Views: 1645

Re: Some Questions About the 707 Family

1: b. Sourced in several places. Not only was the fin height added and the ventral fin added, they also boosted the rudder more because the rudder force with OEI was high. See also this: http://adastron.com/707/qantas/Q-bellows.htm 2. Not 100% sure, but my guess is one of the early BOAC frames. 3. b...

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by LH707330
Thu Oct 29, 2020 3:32 am
Forum: Civil Aviation
Topic: The Airbus A380 Turns 15 Today (April 27)
Replies: 295
Views: 38775

Re: The Airbus A380 Turns 15 Today (April 27)

Question, is Wikipedia correct in that the A350-1000 and A339 have lower FL410 ceilings? It never occurred to me anyone would willingly take another almost 9% increase in drag for end of cruise. Can anyone confirm? Yes, according to the EASA type certificates the A350-1000 and A330 (all variants ex...

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by LH707330
Thu Oct 29, 2020 3:05 am
Forum: Technical/Operations
Topic: How often is the full thrust reverse used vs idle?
Replies: 24
Views: 2756

Re: How often is the full thrust reverse used vs idle?

Thanks for the inputs, this definitely help get an understanding of the variables at play.

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by LH707330
Wed Oct 28, 2020 5:36 am
Forum: Technical/Operations
Topic: How often is the full thrust reverse used vs idle?
Replies: 24
Views: 2756

Re: How often is the full thrust reverse used vs idle?

There isn't really a lot of lift at high speed once the nose wheel is on the ground. The express purpose of the spoilers is to dump lift on touchdown. This plants the mains firmly on the ground, enabling effective braking. Right, I guesstimated 10% for the spoilers, then the wheel brakes do the wor...

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