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by jetmech
Mon Mar 08, 2021 9:57 am
Forum: Technical/Operations
Topic: Comparing Boeing 787 and Airbus A350 wing design
Replies: 19
Views: 2951

Re: Few questions about the A310 (and A300)

Static height brings stiffness with the 4th exponent? For a simple cantilever beam of rectangular cross section acted upon by a point load at the free end, the deflection is given by PL^3 / 3EI; with P being the magnitude of the point load, L the length of the cantilever, E the Modulus of elasticit...

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by jetmech
Sat Mar 06, 2021 6:43 am
Forum: Technical/Operations
Topic: Qatar Airways threatens Pilots for taxiing with both engines
Replies: 39
Views: 7831

Re: Qatar Airways threatens Pilots for taxiing with both engines

I don't think the inboard will be moving backwards. We don't do pivot turns with a stopped main gear leg. True, if you look at the minimum turn radius diagram for the 35K (Fig 4-3-0-991-001-B01 https://www.airbus.com/aircraft/support-services/airport-operations-and-technical-data/aircraft-character...

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by jetmech
Fri Mar 05, 2021 10:56 am
Forum: Technical/Operations
Topic: Qatar Airways threatens Pilots for taxiing with both engines
Replies: 39
Views: 7831

Re: Qatar Airways threatens Pilots for taxiing with both engines

I've observed a number of single engine taxis by various airlines including Qatar. The most glaring problem is the final turn onto the parking bay. If this turn is sharp enough, the inboard engine will physically be moving backwards during the turn. Thus, if the single engine chosen for taxi happens...

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by jetmech
Sun Feb 28, 2021 12:30 am
Forum: Technical/Operations
Topic: Shortest runway airports with regular A380 service
Replies: 27
Views: 5694

Re: Shortest runway airports with regular A380 service

I thought A380 demanded at least 10,500 (at 70 percent load). We recently had 9V-SKQ leave ASP for SYD for a gear swing. She comfortably took off from the 7,999 ft runway and departed with 100 tonnes of fuel aboard due to flying gear down all the way to SYD. This would have put take off weight arou...

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by jetmech
Thu Sep 03, 2020 5:49 am
Forum: Technical/Operations
Topic: Over wing fueling the 747
Replies: 23
Views: 2836

Re: Over wing fueling the 747

Hilarious, really. I’ve seen planes where the overwing ports are actually below the pressure fueling lints, so overwing fueling shorts the potential fuel load. There were definitely overwing fueling ports on the classics, but they were well below the max level of the tank. Usually the overwing acce...

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by jetmech
Wed Jul 01, 2020 1:24 pm
Forum: Technical/Operations
Topic: An-225 pitch trim
Replies: 4
Views: 2034

Re: An-225 pitch trim

Looking at this picture, there seems to be three moveable sections on each side of the horizontal stab. Yes, it's an interesting elevator setup. The outboard sections look to be double or triple hinged. If I’m not mistaken both AN124 and AN225 use a fly by wire flight control system. That would cer...

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by jetmech
Mon Jun 29, 2020 1:28 am
Forum: Technical/Operations
Topic: An-225 pitch trim
Replies: 4
Views: 2034

An-225 pitch trim

Hello All, I'm curious as to how the An-225 achieves longitudinal pitch trim. As far as I can tell, the An-225 has a fixed horizontal stabiliser and hence, the elevators are the only way to provide pitch trim. https://cdn.cnn.com/cnnnext/dam/assets/180831153107-antonov-fedykovych-8.jpg Yet as per th...

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by jetmech
Mon Jun 22, 2020 11:03 am
Forum: Technical/Operations
Topic: A350-1000 fuel burn
Replies: 179
Views: 36356

Re: A350-1000 fuel burn

zeke wrote:
Not really 700 kg is a tad high, you could do that taxi in 10 minutes at the moment with the amount of traffic around at that time of day.

I see. Yes,10 minutes would pretty much cover it. Thanks for the info.

Regards, JetMech

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by jetmech
Mon Jun 22, 2020 8:43 am
Forum: Technical/Operations
Topic: A350-1000 fuel burn
Replies: 179
Views: 36356

Re: A350-1000 fuel burn

Starlionblue wrote:
Either way, for an A359 or A351 a few hundred kilos is most likely not going to have an impact unless your planned fuel is very tight.

Thanks for the info!

Regards, JetMech

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by jetmech
Mon Jun 22, 2020 8:30 am
Forum: Technical/Operations
Topic: A350-1000 fuel burn
Replies: 179
Views: 36356

Re: A350-1000 fuel burn

I can't recall an actual burn for that taxi, but the number seems pretty high. It's just a straight shot down Alpha. Unless you're going at rush hour and know you'll be doing a lot of holding on the way to the hold point. I see. The departure time is scheduled for 2155 but usually ends up being aro...

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by jetmech
Mon Jun 22, 2020 7:25 am
Forum: Technical/Operations
Topic: A350-1000 fuel burn
Replies: 179
Views: 36356

Re: A350-1000 fuel burn

Where do you need 700 kg taxi fuel ? The aircraft / airline in question almost always departs from bay 9 or 10 at Sydney International Terminal. If they are taking off to the north from 34L, they have to taxi almost the full length of 16R-34L. Would 700 kg be a typical fuel consumption for this dis...

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by jetmech
Mon Jun 22, 2020 2:33 am
Forum: Technical/Operations
Topic: A350-1000 fuel burn
Replies: 179
Views: 36356

Re: A350-1000 fuel burn

The way I read that would be an actual tow of approx 285t. That explains the low fuel burn compared to the usual 6.8t at higher weights. Yeah it makes much more sense now. I think we can assume the fuel burn range at 319t would be roughly 6.8 to 7 depending on temperature and everything. I managed ...

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by jetmech
Mon Jun 15, 2020 6:02 am
Forum: Technical/Operations
Topic: Could an airliner save fuel by being unstable
Replies: 22
Views: 3006

Re: Could an airliner save fuel by being unstable

With that, the question is what happens at critical AoA and what stalls first. For swept wing, wing root has to stall first. That creates nose down momentum and helps plane to avoid full stall - if that plane is not 737max. That also allows pushing flight envelope to maximal AoA, hence lower speed ...

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by jetmech
Mon Jun 15, 2020 4:42 am
Forum: Technical/Operations
Topic: Could an airliner save fuel by being unstable
Replies: 22
Views: 3006

Re: Could an airliner save fuel by being unstable

Similar, but not exactly an instability: As far as I understand, canards instead of tail mounted stabilizer could be a fuel saver I think this is an interesting idea. The wings of commercial types need to be bigger than that required to lift the mass of the aircraft due to the negative lift produce...

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by jetmech
Thu Jun 11, 2020 2:30 am
Forum: Technical/Operations
Topic: 747-400 elevator control system
Replies: 14
Views: 2504

Re: 747-400 elevator control system

Standarization of horizontal stabilizer production to -400 standard, with provisions for tail tank installation, requiring re-routing of hydraulic lines.. Thanks. Evidently, the presence of the additional equipment required for the HST precluded the crossing over of hydraulic lines. Regards, JetMech

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by jetmech
Tue Jun 09, 2020 2:00 pm
Forum: Technical/Operations
Topic: A350-1000 fuel burn
Replies: 179
Views: 36356

Re: A350-1000 fuel burn

WOW. So basically at 319t its close to an 18hr bird with a full house of 360 something pax. Wow. From memory it was only around 90 passengers going out but this was made up for with cargo. Colder temps at cruise? That could be part of it. I was thinking they had great tailwinds and took advantage o...

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by jetmech
Tue Jun 09, 2020 2:48 am
Forum: Technical/Operations
Topic: A350-1000 fuel burn
Replies: 179
Views: 36356

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 f...

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by jetmech
Tue May 26, 2020 6:29 am
Forum: Technical/Operations
Topic: 747-400 elevator control system
Replies: 14
Views: 2504

Re: 747-400 elevator control system

From the first 747-400, starting at L/N 696 (and also at several late built 747-200/300 aircraft after L/N 696), the hydraulic system power to the elevators was changed. Any information on why this change was made? I remember being told that it was due to the HST, but this is evidently not so if so...

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by jetmech
Tue May 19, 2020 7:04 am
Forum: Technical/Operations
Topic: Ground height of today’s wide-bodies
Replies: 22
Views: 3762

Re: Ground height of today’s wide-bodies

Starlionblue wrote:
One of the reasons is just differing weights. More weight = more oleo compression.

Exactly. The 777 looks great when it is heavy and everything is compressed down. Same as the 747 which to me, looks quite odd when unladen.

Regards, JetMech

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by jetmech
Tue May 19, 2020 5:44 am
Forum: Technical/Operations
Topic: Ground height of today’s wide-bodies
Replies: 22
Views: 3762

Re: Ground height of today’s wide-bodies

Kno wrote:
It’s part of why I find the 787 so ugly.

Interestingly and conversely, the tall, gangly nosegear of the 777 is something I find very ugly, and the one thing that spoils the beauty of the aircraft.

Regards, JetMech

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by jetmech
Fri May 01, 2020 4:02 am
Forum: Technical/Operations
Topic: N1/N2 RPM question
Replies: 3
Views: 1162

Re: N1/N2 RPM question

. But why is N1 significantly slower (5,000 RPM) compared to the N2 RPM (15,000 RPM)? Does N2 need to rotate faster in order to achieve the necessary amount of compression or something like that? The issue at hand is the tip speed of the various turbine and compressor blades. IIRC, there is an opti...

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by jetmech
Tue Apr 21, 2020 2:04 pm
Forum: Technical/Operations
Topic: 747-200/300 with GE engines...Why the lower fuel capacity?
Replies: 17
Views: 2370

Re: 747-200/300 with GE engines...Why the lower fuel capacity?

Why we're getting a lower fuel capacity with GE? Slightly off topic, the A320 with IAE engines have a slightly less Wing Tank capacity than the CFM counterparts due to the incorportaion of a Dry Bay inside the the Wing cell around the pylon area for additional safety. This can be a reason, however ...

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by jetmech
Sat Apr 18, 2020 11:37 am
Forum: Technical/Operations
Topic: A320 Torque link Damper
Replies: 2
Views: 1640

Re: A320 Torque link Damper

Anyone having internal construction reference of the same? The following provides a diagram of the 737 torque link shimmy damper. I suspect the A320 is similar. https://assets.publishing.service.gov.uk/media/5422f0b8e5274a1317000329/G-BVKC_4-05.pdf Also does it dampen out Vertical(like shock strut)...

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by jetmech
Fri Apr 03, 2020 12:10 am
Forum: Technical/Operations
Topic: Pratt & Whitney JT8D-9A
Replies: 9
Views: 2020

Re: Pratt & Whitney JT8D-9A

My course is in dutch and by "action", I mean "impulse" Jens, the apology should be on my part as it is easy to forget that there are many members on A'net whose first language is not English. does it have an impulse, reaction or a combination of both? According to the following...

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by jetmech
Thu Apr 02, 2020 6:35 am
Forum: Technical/Operations
Topic: Pratt & Whitney JT8D-9A
Replies: 9
Views: 2020

Re: Pratt & Whitney JT8D-9A

I just didn't find the type of inlet, whether the combustion chamber is Reverse, Dual-Dome or Pymene and whether the turbine is an action or reaction turbine. The inlet is most likely a standard, subsonic diverging pitot design except for the Volvo RM8 version of the JT8 which powers the Saab Vigge...

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by jetmech
Wed Feb 05, 2020 10:10 am
Forum: Technical/Operations
Topic: Mechanics of the Parking Brake
Replies: 16
Views: 2134

Re: Mechanics of the Parking Brake

What if the 787 is parked with APU off and no external electric power connected. How does the parking brake remain engaged? I suspect it's to do with the geometry of the gear train which has a ball-screw and nut to generate the required braking force. https://www.flightglobal.com/787-special-system...

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by jetmech
Wed Dec 11, 2019 8:50 am
Forum: Technical/Operations
Topic: Heat Transfer Fluid
Replies: 2
Views: 811

Re: Heat Transfer Fluid

Thanks in advance. The 787 has a number of liquid cooling loops. I'm not sure what cooling fluid is recommended by Boeing; https://www.pd-tech.com/markets/commercial/ Some earlier types used Galden fluid for galley cooling applications; https://www.solvay.com/en/brands/galden-pfpe Regards, JetMech

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by jetmech
Sat Dec 07, 2019 3:35 am
Forum: Technical/Operations
Topic: A350-1000 fuel burn
Replies: 179
Views: 36356

Re: A350-1000 fuel burn

The ramp fuel for the 35K SYD-DOH is between 111-115 tonnes with around 8 tonnes left over on arrival.

Regards, JetMech

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by jetmech
Wed Nov 13, 2019 7:54 am
Forum: Technical/Operations
Topic: Coanda effect and propeller aircraft
Replies: 5
Views: 1104

Re: Coanda effect and propeller aircraft

Does this use of Coanda help the aircraft during cruise phase?] Coanda effect is the phenomenon of a fluid following a concave surface and as such, I don't think it would be overly beneficial in the cruise as the wing is in the clean configuration. Are there other propeller aircraft (like the A400M...

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by jetmech
Sat Nov 09, 2019 8:41 am
Forum: Technical/Operations
Topic: What specific material are the RR Trent XWB fan blades made out of?
Replies: 4
Views: 1277

Re: What specific material are the RR Trent XWB fan blades made out of?

https://www.nipponsteel.com/en/tech/rep ... 106-05.pdf

Regards, JetMech
-->

acavpics wrote:
specific titanium alloy the Trent XWB fan blades are made of and if possible, any links/sources that could help me find more information.


A few more detailed Titanium alloys here;

https://www.nipponsteel.com/en/tech/rep ... 106-05.pdf

Regards, JetMech

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by jetmech
Sat Nov 09, 2019 7:59 am
Forum: Technical/Operations
Topic: What specific material are the RR Trent XWB fan blades made out of?
Replies: 4
Views: 1277

Re: What specific material are the RR Trent XWB fan blades made out of?

specific titanium alloy the Trent XWB fan blades are made of and if possible, any links/sources that could help me find more information. Titanium alloy Ti-6Al-4V would be a good start. Try the search string, "6al 4v titanium fan blade" in Google. The following appears to suggest that the...

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by jetmech
Fri Sep 20, 2019 5:29 am
Forum: Technical/Operations
Topic: Jet engine combustion chambers
Replies: 10
Views: 2648

Re: Jet engine combustion chambers

Does that mean that if one cools the temperature of the expanded hot air inside the burning chamber before it reaches the HP turbine (to make it spin) one looses energy, thus wasting burnt fuel? Is that what you mean? (Interesting stuff, btw...) PS: I'm not an engineer. That's exactly it. Approxima...

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by jetmech
Tue Jan 01, 2019 10:08 am
Forum: Technical/Operations
Topic: Air Pressure Adjacent to Fuselage Side and Tail Cone
Replies: 11
Views: 2718

Re: Air Pressure Adjacent to Fuselage Side and Tail Cone

dlednicer wrote:
Here are CFD pictures of the calculated pressure distribution on a 737-700 at cruise conditions.

Such interesting pictures!

Is that a row of vane vortex generators on the upper tail-cone area above the horizontal stabiliser?

Regards, JetMech

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by jetmech
Tue Dec 25, 2018 5:08 am
Forum: Technical/Operations
Topic: Air Pressure Adjacent to Fuselage Side and Tail Cone
Replies: 11
Views: 2718

Re: Air Pressure Adjacent to Fuselage Side and Tail Cone

What about fuselage sides, supposing these experience zero-incidence airflow over their surfaces. The pressure would be lower than the static air pressure, would it not, because of the high velocity airstream giving rise to a low pressure area immediately adjacent to the fuselage side (at zero airs...

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by jetmech
Sat Dec 15, 2018 5:08 am
Forum: Technical/Operations
Topic: GE9X Maximum Rotor Speed
Replies: 1
Views: 1488

Re: GE9X Maximum Rotor Speed

Does anyone know what the maximum certified RPM of the GE9X's fan is? For the GE90-115B, the EASA states a 5 minute takeoff angular velocity of 2602 RPM (110.5% N1) with interestingly, the same values for max continuous :scratchchin: . https://www.easa.europa.eu/sites/default/files/dfu/EASA%20TCDS%...

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by jetmech
Thu Dec 06, 2018 3:19 am
Forum: Technical/Operations
Topic: GTF vs. triple spool engines
Replies: 33
Views: 3330

Re: GTF vs. triple spool engines

- Fan & LP turbine at 4krpm on spool 1 - IP compressor and IP turbine at 12krpm on spool 2 - HP compressor and turbine at 20+krpm on spool 3 Hmm, might be a tad high with the N2 and N3 RPM's :scratchchin:. They would be closer to 7,000 RPM for IP and 10,600 RPM for HP. https://www.easa.europa.e...

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by jetmech
Wed Nov 28, 2018 6:43 am
Forum: Technical/Operations
Topic: 787 Engine Smoke
Replies: 20
Views: 4512

Re: 787 Engine Smoke

LH707330 wrote:
3-4 quarts total, or per engine?

Per engine. If an engine took a fifth or even sixth quart it was not uncommon.

Regards, Simon

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by jetmech
Tue Nov 27, 2018 2:46 am
Forum: Technical/Operations
Topic: 787 Engine Smoke
Replies: 20
Views: 4512

Re: 787 Engine Smoke

From what you saw, was it mostly a per-flight amount that they consumed, or was it per flight hour, i.e. lots of consumption at cruise as well? I put the oil in them after a flight and 3-4 quarts was a pretty standard uplift. I have no idea when during a flight consumption was highest. Regards, Jet...

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by jetmech
Mon Nov 26, 2018 2:38 am
Forum: Technical/Operations
Topic: 787 Engine Smoke
Replies: 20
Views: 4512

Re: 787 Engine Smoke

I've seen this on the 340s from some of the back seat rows, that little pipe has a grayish tint on the inside. Anybody know why the CFM56-5C burns so much oil? I've heard the -7s on the 737s burn a decent amount as well. Continuing:: High eng oil consumption may have another reasons, like bad seali...

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by jetmech
Sat Nov 17, 2018 3:01 am
Forum: Technical/Operations
Topic: 787 Engine Smoke
Replies: 20
Views: 4512

Re: 787 Engine Smoke

Granted, each manufacturer has their own approach to venting. But still. Our B744 AMM says the CF6 vents directly into the exhaust. On the CFMs, GEs, and PWs, there’s that huge hole at the back of the exhaust and the oil is burnt off that way. I always see quite a bit of coked up oil residue on the...

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by jetmech
Tue Nov 13, 2018 2:18 am
Forum: Technical/Operations
Topic: 787 Engine Smoke
Replies: 20
Views: 4512

Re: 787 Engine Smoke

viewtopic.php?t=761787

Regards, JetMech
-->

seb146 wrote:
What exactly is it?


viewtopic.php?t=761787

Regards, JetMech

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by jetmech
Wed Sep 26, 2018 5:38 am
Forum: Technical/Operations
Topic: What is this thing in the 747 cockpit?
Replies: 25
Views: 5040

Re: What is this thing in the 747 cockpit?

LuiePL wrote:
It looks like it's something to align the plane.


The 747 also has crosses on the windshield pillars that serve the same purpose as shown below;



This photo shows a 747 cockpit equipped with both the crosses and balls;



Regards, JetMech

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by jetmech
Sun Jun 24, 2018 11:29 am
Forum: Technical/Operations
Topic: What makes the engine physically go faster?
Replies: 17
Views: 1990

Re: What makes the engine physically go faster?

Doesn't richer fuel result in "cooler fuel" since the heat is being distributed among more fuel? For a spark ignition piston engine, a richer mixture does cool things down, but this is due to the phase change (liquid to vapour) of the excess fuel taking heat from the combustion process. R...

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by jetmech
Sun Jun 24, 2018 11:15 am
Forum: Technical/Operations
Topic: Windmilling with a tail wind & lubrication
Replies: 8
Views: 1631

Re: Windmilling with a tail wind & lubrication

But rolling dry will kill a bearing regardless of speed. I'm guessing that there is enough retained oil at all times that this isn't an issue. Indeed. Not surprisingly, a big killer of rolling element bearings is when the balls or rollers skid along the races instead of rolling. When changing wheel...

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by jetmech
Sun Jun 24, 2018 11:01 am
Forum: Technical/Operations
Topic: NDT-Boroscope
Replies: 8
Views: 886

Re: NDT-Boroscope

Here, the AMT does the whole thing. No requirement for QC, unless specifically called for in a special inspection. This is similar to Australia. That being said, we had standalone boroscope crews who did the inspections, but I don't recall there being any special qualification required. There was h...

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by jetmech
Wed Jun 20, 2018 1:15 am
Forum: Technical/Operations
Topic: Windmilling with a tail wind & lubrication
Replies: 8
Views: 1631

Re: Windmilling with a tail wind & lubrication

Is there even an oil pump on N2, such that N2 rolling backwards would even matter? Most commercial turbofans have the accessory gearbox and hence oil pumps driven by the high pressure spool which would thus be N2 (GE, P&W, CFM) or N3 (RR), but as pointed out by fr8mech, what you are seeing is t...

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by jetmech
Thu May 10, 2018 4:09 am
Forum: Technical/Operations
Topic: Engine Fan Blade Rub
Replies: 26
Views: 5073

Re: Engine Fan Blade Rub

The P&W shrouds have several grooves milled into them going around the circumference of the fan blade path. They are in segments that are about eight to ten inches long and are bonded into place. To me, they look like caramel colored Masonite board. Not sure what they are made of. In all my yea...

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by jetmech
Wed May 09, 2018 6:30 am
Forum: Technical/Operations
Topic: Engine Fan Blade Rub
Replies: 26
Views: 5073

Re: Engine Fan Blade Rub

gregorygoodwin wrote:
On our P&W engines, they use a grooved fiberboard type of material under the fan path.


Perhaps P&W were trying to provide a labyrinth seal type configuration to further minimise tip leakage?

Regards, JetMech

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by jetmech
Sun May 06, 2018 8:11 am
Forum: Technical/Operations
Topic: Engine Fan Blade Rub
Replies: 26
Views: 5073

Re: Engine Fan Blade Rub

Is there a video on youtube I couldn't find anything on Youtube unfortunately. And what do you mean "remove material if need be." As others have noted, the abradable liner is made of a material that is softer than the fan blades. Thus, if the blade tip should contact the abradable liner d...

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by jetmech
Fri May 04, 2018 4:08 am
Forum: Technical/Operations
Topic: Engine Fan Blade Rub
Replies: 26
Views: 5073

Re: Engine Fan Blade Rub

I know fan blades have a very minimal clearance from the engine cowling, but can it ever rub against the cowling interior during turbulence or anything? And if it could rub against the cowling, what would happen? Yes they can. The fan casing is made with an abradable liner such that the tips of the...

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