Search found 2312 matches

  • 1
  • 2
  • 3
  • 4
  • 5
  • 47
by LH707330
Wed Aug 12, 2020 5:21 pm
Forum: Technical/Operations
Topic: Hydrogen flying wing
Replies: 19
Views: 1474

Re: Hydrogen flying wing

If green hydrogen is 6-10x the price of Jet-A, then you're better off using any surplus wind power to synthesize hydrocarbon fuels or convert biomass into some drop-in fuels. Once enough money is thrown at it, price will come down. Solar electricity, batteries, mobiles, planes and everything else h...

Jump to post
by LH707330
Sat Aug 08, 2020 6:33 pm
Forum: Technical/Operations
Topic: Hydrogen flying wing
Replies: 19
Views: 1474

Re: Hydrogen flying wing

If green hydrogen is 6-10x the price of Jet-A, then you're better off using any surplus wind power to synthesize hydrocarbon fuels or convert biomass into some drop-in fuels.

Jump to post
by LH707330
Fri Jul 31, 2020 10:55 pm
Forum: Technical/Operations
Topic: Question Regarding 737 Classic Wing
Replies: 5
Views: 1165

Re: Question Regarding 737 Classic Wing

The Classic had a couple of changes from the Jurassic: more chord and a slightly longer span, see here for details: http://www.b737.org.uk/737classic.htm That aft pylon does have flap mechanisms in it, probably a similar design to the Jurassics, which is why they kept it there. The NG went to a new ...

Jump to post
by LH707330
Fri Jul 31, 2020 10:51 pm
Forum: Technical/Operations
Topic: B752 Engine Options?
Replies: 17
Views: 2362

Re: B752 Engine Options?

Efficiency goes to the Pratt by 2-3 percent, IINM.
Performance is a bit of a vague term, but the RR had a higher max thrust version and spools faster due to the three-shaft design.

Jump to post
by LH707330
Fri Jul 31, 2020 10:41 pm
Forum: Technical/Operations
Topic: Landing Gear retraction
Replies: 11
Views: 2040

Re: Landing Gear retraction

Also, most airliners (exception: some early 727s that then mostly had them yanked because they were not super useful) don't have brakes on the nose gear, so without the snubbers they'd just keep spinning.

Jump to post
by LH707330
Sat Jul 18, 2020 6:32 pm
Forum: Technical/Operations
Topic: Most obvious way to significantly cut boarding time
Replies: 45
Views: 5449

Re: Most obvious way to significantly cut boarding time

I wonder how long it'll take for an airline to subdivide the overheads and make them bookable. Chop them into chunks with dividers, and sell them. Your seat assignment is 22A, and your bag assignment is 22X. That way, disputes are easily resolved and the rush to board early goes away. Now you can im...

Jump to post
by LH707330
Wed Jul 15, 2020 4:00 am
Forum: Technical/Operations
Topic: NW DC-10-40 vs DC-10-30
Replies: 35
Views: 3668

Re: NW DC-10-40 vs DC-10-30

Which shows how technically illiterate airline management is. The GE was the better engine. What would make the GE better than the PW for the DC10? Curious to get your take on it. If you stare at enough pictures, you can also spot the difference by looking at the #1 or #3 engines: the GE is a bit l...

Jump to post
by LH707330
Wed Jun 10, 2020 1:50 am
Forum: Technical/Operations
Topic: A350-1000 fuel burn
Replies: 114
Views: 16723

Re: A350-1000 fuel burn

That is insane though. 77W with basically equal or less than 77E and 343 fuel burn. WOW. So basically at 319t its close to an 18hr bird with a full house of 360 something pax. Wow. Curious about that last comparison between the 77W, 77E, and 343, are you saying they all burn around the same? I beli...

Jump to post
by LH707330
Tue Jun 09, 2020 4:22 am
Forum: Technical/Operations
Topic: Landing - Thrust Reverse and Brake
Replies: 33
Views: 2275

Re: Landing - Thrust Reverse and Brake

It's rare that full braking and full reverse are used. What typically happens is that the crew selects an autobrake setting that will get them stopped where they need to be, and then uses that coupled with idle reverse. The computer applies brakes to get to the desired deceleration rate, so if the p...

Jump to post
by LH707330
Tue Jun 09, 2020 4:09 am
Forum: Technical/Operations
Topic: A350-1000 fuel burn
Replies: 114
Views: 16723

Re: A350-1000 fuel burn

I just had a SYD-DOH A35K flight with a ramp fuel load of 98.3 tonnes (trip fuel of 91.4 tonnes). Interestingly, the RTOW (316 tonnes) was close to MTOW (318 tonnes) and the flight time was 14 hr 15 min which is close to typical. What would have allowed for such a low fuel load when the usual ramp ...

Jump to post
by LH707330
Sat Jun 06, 2020 3:13 am
Forum: Technical/Operations
Topic: Supersonic Engine effeciency
Replies: 15
Views: 3184

Re: Supersonic Engine effeciency

Concorde was great from a thermodynamic efficiency standpoint, what made it inefficient was the awful L/D that forced the engines to do so much more work.

Jump to post
by LH707330
Sat Jun 06, 2020 3:09 am
Forum: Civil Aviation
Topic: Aerion moves forward with supersonic AS2 for 2024, unveils new final design
Replies: 113
Views: 16981

Re: Aerion moves forward with supersonic AS2 for 2024, unveils new final design

This is an exciting development, curious to see how it pans out.

Regarding the pollution, I definitely hope that we get sustainable fuels soon. I'm curious, what's a pallpark percentage of fuel as total operating cost for a bizjet? If SAF is 50% more, what does that do to the TOC?

Jump to post
by LH707330
Thu Jun 04, 2020 5:06 pm
Forum: Technical/Operations
Topic: Landing wind direction
Replies: 28
Views: 2704

Re: Landing wind direction

More reading on the topic: https://www.boldmethod.com/blog/lists/2018/09/six-dangers-of-tailwinds-during-takeoff-and-landing/ https://www.boldmethod.com/learn-to-fly/maneuvers/why-landing-with-a-tailwind-can-increase-your-risk-of-a-landing-accident/ https://www.airliners.net/forum/viewtopic.php?t=73...

Jump to post
by LH707330
Tue Jun 02, 2020 3:37 am
Forum: Technical/Operations
Topic: Landing wind direction
Replies: 28
Views: 2704

Re: Landing wind direction

Another consideration, given some aircraft that have a 20 knot tailwind for landing, is tire speed. Most heavy jets have tire maximum speed in excess of 230 kts ground speed. Where "on time performance" is so important, and a tailwind landing can accomplish this, the tailwind landing is a...

Jump to post
by LH707330
Mon May 11, 2020 11:35 pm
Forum: Technical/Operations
Topic: 747-400 with non-FADEC engines?
Replies: 13
Views: 1849

Re: 747-400 with non-FADEC engines?

Some of the late 747-300s were fitted with CF6-80C2 engines that lacked FADEC, so you could notionally get the hardware from that setup and stick it into a 400. That said, no beancounter would sign off on it, so unless you had several (tens of?) millions burning a hole in your pocket, it's not gonna...

Jump to post
by LH707330
Sat May 09, 2020 9:33 pm
Forum: Technical/Operations
Topic: CF6-50 vs CF6-80
Replies: 6
Views: 1524

Re: CF6-50 vs CF6-80

There are really four versions in there, the 50, 80A, 80C2, and 80E. In a nutshell, here's an overview: 50: baseline 80A: compact layout version 80C2: new core and bigger fan 80E: similar architecture to 80C2 with some other tweaks (this helped them be first to market, but cost them later on agains...

Jump to post
by LH707330
Fri May 08, 2020 11:22 pm
Forum: Technical/Operations
Topic: CF6-50 vs CF6-80
Replies: 6
Views: 1524

Re: CF6-50 vs CF6-80

There are really four versions in there, the 50, 80A, 80C2, and 80E. In a nutshell, here's an overview: 50: baseline 80A: compact layout version 80C2: new core and bigger fan 80E: similar architecture to 80C2 with some other tweaks (this helped them be first to market, but cost them later on against...

Jump to post
by LH707330
Fri May 08, 2020 11:15 pm
Forum: Technical/Operations
Topic: PW4000-94 and CF6-80C2 Comparison
Replies: 6
Views: 1434

Re: PW4000-94 and CF6-80C2 Comparison

Well the CF6 ended up being the most powerful of those level of engines and it also is louder than the PW4000-94 which makes sense. The most powerful engine in this case is simply the biggest one. The CF6 basically began as the CF6 and got changed here and there every time there was the need. The P...

Jump to post
by LH707330
Wed May 06, 2020 11:47 pm
Forum: Technical/Operations
Topic: PW4000-94 and CF6-80C2 Comparison
Replies: 6
Views: 1434

Re: PW4000-94 and CF6-80C2 Comparison

Why is it that GE built so many more stages into their engine and made it so much longer in the process? It was obviously the best-selling engine of that generation, so they were doing something right, but what? Its what makes it the 4 time world discus throwing champion. Ha ha, clever. See this ol...

Jump to post
by LH707330
Wed May 06, 2020 11:44 pm
Forum: Technical/Operations
Topic: Cost of “fuel tankering”?
Replies: 94
Views: 7131

Re: Cost of “fuel tankering”?

The way to address this, as some have said, is to implement a CO2 tax on fossil fuels. That will force users to reduce their consumption in a way that makes the most economic sense, in this case making tankering relatively more expensive. Taxing excess leftover fuel might create perverse incentives...

Jump to post
by LH707330
Wed May 06, 2020 11:41 pm
Forum: Technical/Operations
Topic: 747-400 horizontal stabilizer tank question
Replies: 22
Views: 3248

Re: 747-400 horizontal stabilizer tank question

Call it maybe 10 kg of sealant, plus fuel lines and pumps, gives a differential weight of maybe 100 kg for the whole system. As far as the stabilizer weight, you'd have to sort out what the spars and wing skins weigh.

Jump to post
by LH707330
Wed May 06, 2020 3:02 am
Forum: Technical/Operations
Topic: PW4000-94 and CF6-80C2 Comparison
Replies: 6
Views: 1434

PW4000-94 and CF6-80C2 Comparison

The other thread about the DC10 engines and the 747 wing tank capacities got me thinking about the era of the "commodity engines," where every widebody frame had either 2, 3, or 4 of whatever the highest-thrust engine of the time was. In comparing the PW4000-94 and the CF6-80C2, I saw they...

Jump to post
by LH707330
Wed May 06, 2020 2:44 am
Forum: Technical/Operations
Topic: 747-400 horizontal stabilizer tank question
Replies: 22
Views: 3248

Re: 747-400 horizontal stabilizer tank question

Not much, really. It's just a sealed interspar region with a few bits of plumbing.

Jump to post
by LH707330
Fri Apr 24, 2020 6:06 pm
Forum: Technical/Operations
Topic: Boeing 777 PIP 2.0 2016
Replies: 7
Views: 1757

Re: Boeing 777 PIP 2.0 2016

I think a lot of the weight removal is likely not retrofittable if it was a structural reduction.

Jump to post
by LH707330
Fri Apr 24, 2020 6:03 pm
Forum: Technical/Operations
Topic: What made the 737 more "upgradable" than the 727?
Replies: 37
Views: 4504

Re: What made the 737 more "upgradable" than the 727?

The VC10 and B720B have little in common other than the fact they are both jet airliners. Maybe the 707-320B and Suoer VC10 would be a closer comparison? Love the VC10:) Both were designed to have good performance at the expense of seat mile cost, especially relative to their larger siblings you me...

Jump to post
by LH707330
Fri Apr 24, 2020 6:00 pm
Forum: Technical/Operations
Topic: What made the 737 more "upgradable" than the 727?
Replies: 37
Views: 4504

Re: What made the 737 more "upgradable" than the 727?

The tail mounted engines were NOT for FOD protection. There is no certification standard for FOD protection. They were done for 1/ field performance out of LGA; 2/ accommodate 3 engines to lower take-off weather minimums as existed in 1960 (3 engines reduced weather to 1/2 mile as opposed to twins ...

Jump to post
by LH707330
Mon Apr 20, 2020 6:21 pm
Forum: Technical/Operations
Topic: What made the 737 more "upgradable" than the 727?
Replies: 37
Views: 4504

Re: What made the 737 more "upgradable" than the 727?

There are several reasons that this would not have been a good economic idea, although possible as an engineering exercise. Start with the wing: it's got a 35-degree sweep and triple slotted flaps so it could go both fast and slow. This means it's heavy. All of the replacements (A320, 757, 734/738)...

Jump to post
by LH707330
Sun Apr 19, 2020 6:36 pm
Forum: Technical/Operations
Topic: What made the 737 more "upgradable" than the 727?
Replies: 37
Views: 4504

Re: What made the 737 more "upgradable" than the 727?

There are several reasons that this would not have been a good economic idea, although possible as an engineering exercise. Start with the wing: it's got a 35-degree sweep and triple slotted flaps so it could go both fast and slow. This means it's heavy. All of the replacements (A320, 757, 734/738) ...

Jump to post
by LH707330
Thu Apr 16, 2020 2:48 am
Forum: Technical/Operations
Topic: Alcoholic beverage consumption in-flight
Replies: 13
Views: 2731

Re: Alcoholic beverage consumption in-flight

Last year I was at an AA lounge at DFW during a weekday morning and I was amazed at how many people were drinking beer at 0900 hours. In airports and in passenger cabins it's always 1700, is what I've been told! In all seriousness though, the US is pretty lopsided: https://www.washingtonpost.com/ne...

Jump to post
by LH707330
Sat Apr 11, 2020 4:11 pm
Forum: Technical/Operations
Topic: How difficult it is to upscaled GTF
Replies: 30
Views: 3398

Re: How difficult it is to upscaled GTF

Yeah, drag and weight go up, but propoulsive efficiency and thermodynamic efficiency improve. Think of it this way: some lines go up and right, others go down and right. You add them all together, and get a U-shape, then pick the bottom of the U. This is obviously a slight simplification, but you g...

Jump to post
by LH707330
Sat Apr 11, 2020 1:17 am
Forum: Technical/Operations
Topic: 747SP fifth pod ?
Replies: 32
Views: 3266

Re: 747SP fifth pod ?

Anyone know if this sub type was certified for fifth pod engine ferry and if it was ever done ? Syrian 747SP, YK-AHA, 1999-09-01, MUC, with 5th pod installed : https://www.747sp.com/wp-content/gallery/21174-284/21174_yk-aha_old5engines.jpg See : https://www.747sp.com/747sp-production-list/21174-284...

Jump to post
by LH707330
Sat Apr 11, 2020 1:09 am
Forum: Technical/Operations
Topic: How difficult it is to upscaled GTF
Replies: 30
Views: 3398

Re: How difficult it is to upscaled GTF

Larger turbofan/cowling diameters don't require a reduction in cruise speed, so there's no further advantage or disadvantage for slower planes or faster planes. But don't they increase drag as well? Increasing diameter by 10% increases inlet area by over 20%. And I believe engines are more turbulen...

Jump to post
by LH707330
Thu Apr 09, 2020 5:18 am
Forum: Technical/Operations
Topic: How difficult it is to upscaled GTF
Replies: 30
Views: 3398

Re: How difficult it is to upscaled GTF

If bypass ratios are increasing, isn't the advantage for the slower A330 more than for the faster B787? Larger turbofan/cowling diameters don't require a reduction in cruise speed, so there's no further advantage or disadvantage for slower planes or faster planes. Higher BPR engines suffer from mor...

Jump to post
by LH707330
Thu Apr 09, 2020 5:16 am
Forum: Technical/Operations
Topic: A330 vs A330NEO wing area question/typo?
Replies: 6
Views: 1419

Re: A330 vs A330NEO wing area question/typo?

I saw this somewhere before about a month ago. No chord extension, so with the same measurement approach, it should be pretty similar. Something in that reference is off. OP, what's the source doc for it?

Jump to post
by LH707330
Fri Mar 27, 2020 1:11 am
Forum: Technical/Operations
Topic: A330-300 vs. A340-300 range
Replies: 44
Views: 9231

Re: A330-300 vs. A340-300 range

In the land of fantasy planes the A342 with PW1100g would be a monster range machine (too much maybe). If one were to upgrade as such it would likely be better to use 300 and 500 lengths with original wings. Such a machines fuel burn figures would have been at home with the 787/A330NEO/A350. Some w...

Jump to post
by LH707330
Thu Mar 19, 2020 6:16 pm
Forum: Technical/Operations
Topic: Silly designs in otherwise great aircraft
Replies: 56
Views: 7748

Re: Silly designs in otherwise great aircraft

CRJ100/200 had a cup holder that was too small for a can of soda. As the CRJ100 probably has a nearly identical cockpit to a Challenger which went into service in the 80's: Soda cans in Canada were smaller than the US until 1990 or so... http://www.coke-cans.com/canada.html I always wondered why Ca...

Jump to post
by LH707330
Wed Mar 18, 2020 9:55 pm
Forum: Technical/Operations
Topic: 747 vs 777 new flaps
Replies: 3
Views: 1479

Re: 747 vs 777 new flaps

The 748 kept the same planform as the 744, and hence had more constraints than the 779, which has a completely different wing. If the 748 team had a bigger budget, they probably would have reduced the sweep angle and reimagined the whole setup.

Jump to post
by LH707330
Sat Mar 14, 2020 9:32 pm
Forum: Technical/Operations
Topic: (Hypothetical) Water injection on high-bypass engine
Replies: 34
Views: 4441

Re: (Hypothetical) Water injection on high-bypass engine

Now let's say you're putting (on takeoff) 5 CFM before the LPC, an additional 5 CFM into the combustion chamber, 145 CFM after the LPT inside the core, and 145 CFM into the bypass. Could 10 CFM of water in the combustion chamber cause the engine to flame out? 10 CFM is 17t/hr if my numbers below ar...

Jump to post
by LH707330
Fri Mar 13, 2020 4:20 pm
Forum: Technical/Operations
Topic: B767-300 Door Configurations
Replies: 6
Views: 1322

Re: B767-300 Door Configurations

While there have been many discussions on the topic of the multiple door configurations of the B767-300, I have a couple of questions that so far I’ve not been able to dig up answers to: 1) Is there a complete list available of all of the frames still active that have an L2 door forward of the wing...

Jump to post
by LH707330
Fri Mar 13, 2020 4:18 pm
Forum: Technical/Operations
Topic: (Hypothetical) Water injection on high-bypass engine
Replies: 34
Views: 4441

Re: (Hypothetical) Water injection on high-bypass engine

Ahh, I see what's going on here. There are two things to take into consideration: 1. The water should be injected into the core, which has a faster output, so your mass flow at that higher rate will give you more thrust 2. The water improves the thermodynamic efficiency of the core due to the laten...

Jump to post
by LH707330
Fri Mar 13, 2020 3:00 am
Forum: Technical/Operations
Topic: (Hypothetical) Water injection on high-bypass engine
Replies: 34
Views: 4441

Re: (Hypothetical) Water injection on high-bypass engine

And after doing a detailed analysis on multiple aircraft, I noted that water injection, whether in the core or in the bypass, only gives enough of an improvement at high payloads as that is when the thrust increase offsets the increase in TOW. For lightly-loaded/empty planes, it actually detracts f...

Jump to post
by LH707330
Thu Mar 12, 2020 3:14 pm
Forum: Technical/Operations
Topic: 787 Fuel Efficency?
Replies: 2
Views: 950

Re: 787 Fuel Efficency?

Airbus claims hat their own neo is something like 14% better than the ceo, with 11% from the engines. 12-17% depending on the config doesn't seem too far off, and still gives the 332 a decent 5ish percent margin over the 763.

Jump to post
by LH707330
Thu Mar 12, 2020 4:34 am
Forum: Civil Aviation
Topic: What was the rationale for 2-5-2 configuration on older widebodies?
Replies: 77
Views: 14353

Re: What was the rationale for 2-5-2 configuration on older widebodies?

If he plane is half empty, then I like the 3-3-3, because it means 3 people per row can sleep vs 1 or 2 in 2-5-2. I've gotten great sleep on 787s and A350s when I get an empty 3-pack and can stretch out.

Jump to post
by LH707330
Thu Mar 12, 2020 4:09 am
Forum: Technical/Operations
Topic: (Hypothetical) Water injection on high-bypass engine
Replies: 34
Views: 4441

Re: (Hypothetical) Water injection on high-bypass engine

And after doing a detailed analysis on multiple aircraft, I noted that water injection, whether in the core or in the bypass, only gives enough of an improvement at high payloads as that is when the thrust increase offsets the increase in TOW. For lightly-loaded/empty planes, it actually detracts f...

Jump to post
by LH707330
Sat Mar 07, 2020 10:21 pm
Forum: Technical/Operations
Topic: How does aviation tackle climate change?
Replies: 133
Views: 27044

Re: How does aviation tackle climate change?

https://medium.com/@merlinwoodman/why-a ... cdcd6c22f7
-->

Here's an idea I came across recently: have the airlines directly sell sustainable fuels: https://medium.com/@merlinwoodman/why-a ... cdcd6c22f7

Jump to post
by LH707330
Sat Mar 07, 2020 10:16 pm
Forum: Technical/Operations
Topic: (Hypothetical) Water injection on high-bypass engine
Replies: 34
Views: 4441

Re: (Hypothetical) Water injection on high-bypass engine

Thanks, that was an informative article. However, I don't understand why the SFC improves only by about 3-4 percent for LPC injection (and negative for combustor injection) when the water-fuel mix is in the vicinity of 1:2 or 1:1. You'd think that with a 33-50 percent reduction in fuel, the percent...

Jump to post
by LH707330
Wed Feb 26, 2020 7:46 pm
Forum: Technical/Operations
Topic: (Hypothetical) Water injection on high-bypass engine
Replies: 34
Views: 4441

Re: (Hypothetical) Water injection on high-bypass engine

No, the ones done in the past were just less sophisticated, it is possible to do a water injection system with little or no smoke and overall performance improvements. Check this out: https://mdao.grc.nasa.gov/publications/SAE_H2O_Paper_7_20_04.pdf Thanks, that was an informative article. However, ...

Jump to post
by LH707330
Tue Feb 18, 2020 8:20 pm
Forum: Technical/Operations
Topic: (Hypothetical) Water injection on high-bypass engine
Replies: 34
Views: 4441

Re: (Hypothetical) Water injection on high-bypass engine

If a water-injection system were to be installed on an aircraft high-bypass turbofan, where would the injectors be placed? My guess is probably in the core, just after the low-pressure turbine, or in the bypass duct. Probably not injecting it into the combustion chamber, as cooling the flame would ...

Jump to post
by LH707330
Tue Feb 11, 2020 11:29 pm
Forum: Technical/Operations
Topic: NMA/MOM/797 variant performance analysis
Replies: 151
Views: 13551

Re: NMA/MOM/797 variant performance analysis

Fred, thanks for putting this together. Looks like a 6W 757 replacement is likely the way to go of these options. Now my question is whether the OEW/m^2 compares favorably to an A321, and whether this new design has enough of a per-seat advantage. You have numbers on that?

Jump to post
by LH707330
Sun Feb 09, 2020 2:46 am
Forum: Technical/Operations
Topic: Worth it being a pilot?
Replies: 30
Views: 2838

Re: Worth it being a pilot?

That is 100 percent my opinion based on what I have seen as an instructor and volunteer at one of the busiest GA airports in the country. My generation (Gen Z) will never be able to pay 100k-900k for a single engine piston aircraft compared to previous generations having reduced costs when it comes...

Jump to post
  • 1
  • 2
  • 3
  • 4
  • 5
  • 47