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by kalvado
Thu Feb 02, 2023 6:02 pm
Forum: Technical/Operations
Topic: ETOPS In Flight Shutdown Statistics
Replies: 46
Views: 3419

Re: ETOPS In Flight Shutdown Statistics

IIRC the CSM/G is also a dinky 5kw unit. Barely enough to keep the battery charged, the Captains instruments and a few of the flight control computers operating. I've never known of an incident whereby any airplane was down to that generator. If you're down to that, you're in serious trouble. This ...

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by kalvado
Thu Feb 02, 2023 4:47 pm
Forum: Technical/Operations
Topic: Engine Derates and top-of-climb power
Replies: 73
Views: 3432

Re: Engine Derates and top-of-climb power

This is drivel, the jet exhaust over the tailplane as cited above is not flutter. Lots of aircraft types experience similar. Your posts are just red herrings, and do not address the claim at all. I was very familiar with flutter, in air, in water, and in space. The engineering principles have not c...

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by kalvado
Thu Feb 02, 2023 3:21 pm
Forum: Technical/Operations
Topic: Engine Derates and top-of-climb power
Replies: 73
Views: 3432

Re: Engine Derates and top-of-climb power

Simple, almost incorrect example which gives you the flavor though: Imagine an airfoil in the flow, which vibrates so that AoA is changing. Without airflow, you have a deflection, a corresponding restoring elastic force, and airfoil oscillates around some central position. Frequency, amplitude, all ...

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by kalvado
Thu Feb 02, 2023 3:08 pm
Forum: Technical/Operations
Topic: Engine Derates and top-of-climb power
Replies: 73
Views: 3432

Re: Engine Derates and top-of-climb power

Excessively immature. I am very familiar with the difference between vibration and flutter, I have provided the definition of flutter. Many many moons ago I used to do ground vibration testing using Brüel & Kjær shakers and accelerometers connected to a HP FFT system doing modal analysis on a H...

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by kalvado
Thu Feb 02, 2023 4:12 am
Forum: Technical/Operations
Topic: Engine Derates and top-of-climb power
Replies: 73
Views: 3432

Re: Engine Derates and top-of-climb power

What is the difference between flutter and vibration in the wind from your perspective? Flutter is a specific engineering, it means an unstable, self-excited structural oscillation at a definite frequency where energy is extracted from the airstream by the motion of the structure. It can occur in b...

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by kalvado
Thu Feb 02, 2023 12:57 am
Forum: Technical/Operations
Topic: Engine Derates and top-of-climb power
Replies: 73
Views: 3432

Re: Engine Derates and top-of-climb power

GalaxyFlyer wrote:
Flutter is a harmonic, aerodynamic vibration isn’t.

Wut?

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by kalvado
Wed Feb 01, 2023 10:05 pm
Forum: Technical/Operations
Topic: Engine Derates and top-of-climb power
Replies: 73
Views: 3432

Re: Engine Derates and top-of-climb power

It’s false. Flutter is the interaction between the airflow over an aero structure and how it excites the inherent structural modes are excited. The aero structure does not know the difference between air coming from an engine or from free stream flow. The 77F/77L can have either a General Electric ...

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by kalvado
Wed Feb 01, 2023 12:53 am
Forum: Technical/Operations
Topic: Engine Derates and top-of-climb power
Replies: 73
Views: 3432

Re: Engine Derates and top-of-climb power

Fun fact: The 777-200 LR GE90-115 was down rated to 110,000 lbs of thrust and designated the GE90-110. Exact same engine, just an artificially imposed limitation This limitation was imposed because testing revealed that 115,000 lbs of thrust moved so much air that flutter was induced on the elevato...

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by kalvado
Thu Jan 26, 2023 5:49 pm
Forum: Technical/Operations
Topic: Insulation blankets
Replies: 8
Views: 1382

Re: Insulation blankets

https://www.jm.com/content/dam/jm/globa ... _Sheet.pdf
the R values are in 3-5 range.
-->

SteelChair wrote:
As I recall, they are very thin. Surprisingly thin. They probably have a very small R value.

If this datasheet is of any relevance:
https://www.jm.com/content/dam/jm/globa ... _Sheet.pdf
the R values are in 3-5 range.

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by kalvado
Thu Jan 26, 2023 2:33 pm
Forum: Technical/Operations
Topic: Engine Derates and top-of-climb power
Replies: 73
Views: 3432

Re: Engine Derates and top-of-climb power

Hence why cruise power is pretty near maximum. Near maximum by what metric? Certainly not by shaft power or fuel flow. Near maximum achievable at that altitude? From what I get from pilots here, if there is enough power to climb - it makes economic sense to do so.. Would N1 and/or EGT be near maxim...

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by kalvado
Wed Jan 25, 2023 10:26 pm
Forum: Technical/Operations
Topic: Engine Derates and top-of-climb power
Replies: 73
Views: 3432

Re: Engine Derates and top-of-climb power

And what about temperatures? Those should be significant for engine wear. Of course, if temperature is communicated to pilots to begin with... Not sure what you're trying to get at here but EGT isn't hidden from the crew, at least not in any types I've flown. Going by the Trent 800 publication reco...

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by kalvado
Wed Jan 25, 2023 10:25 pm
Forum: Technical/Operations
Topic: ETOPS In Flight Shutdown Statistics
Replies: 46
Views: 3419

Re: ETOPS In Flight Shutdown Statistics

What you say is second approach becomes dominant. As a passenger who prefers getting to the destination in one piece (and hence from the regulator standpoint) that's fine as long as it works. So shutdown statistics in that monitoring scenario may not tell airline cost story, but it definitely tells...

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by kalvado
Wed Jan 25, 2023 8:35 pm
Forum: Technical/Operations
Topic: Engine Derates and top-of-climb power
Replies: 73
Views: 3432

Re: Engine Derates and top-of-climb power

That is a good way of putting it. Engines lose thrust with altitude due to lower mass flow in thinner air. Hence why cruise power is pretty near maximum. Near maximum by what metric? Certainly not by shaft power or fuel flow. Near maximum achievable at that altitude? From what I get from pilots her...

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by kalvado
Wed Jan 25, 2023 2:20 pm
Forum: Technical/Operations
Topic: ETOPS In Flight Shutdown Statistics
Replies: 46
Views: 3419

Re: ETOPS In Flight Shutdown Statistics

It got me to thinking, what are the real world statistics of in flight engine shutdowns (IFSD) on ETOPS maintained airplanes? It looks like SYD-AKL requires 90 minute ETOPS. The stats these days are rather meaningless, with all the engine monitoring that is done engines are pulled before they fail....

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by kalvado
Wed Jan 25, 2023 2:10 pm
Forum: Technical/Operations
Topic: Engine Derates and top-of-climb power
Replies: 73
Views: 3432

Re: Engine Derates and top-of-climb power

On all Boeing non-737 models climb derates are a fixed percentage of full climb there. There are two climb derate settings - CLB 1 and CLB 2. The precent derates are customer selectable, but they are usually 10% and 20%. The 737 is a bit different and I’m not as familiar with it. Thanks for confirm...

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by kalvado
Tue Jan 24, 2023 12:24 pm
Forum: Technical/Operations
Topic: Engine Derates and top-of-climb power
Replies: 73
Views: 3432

Re: Engine Derates and top-of-climb power

There's a thread somewhere about derates on here. Most of them wash out in the 8-10k foot range and then resume the normal climb schedule. I'm pretty sure that only applies to the dense air conditions where it gets the most strain. Higher up you want to allow higher settings because the engine is m...

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by kalvado
Sun Jan 22, 2023 1:21 pm
Forum: Technical/Operations
Topic: True Altitude
Replies: 16
Views: 1279

Re: True Altitude

kalvado wrote:
Advantage of pressure is that it is easy to agree upon, and updates are not expected...

Thinking about it, altitude-to-pressure conversion also can be messy. Probably somewhere in IATA documents, there is a formula describing that conversion, which everyone reluctantly agreed upon.

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by kalvado
Sun Jan 22, 2023 1:12 pm
Forum: Technical/Operations
Topic: True Altitude
Replies: 16
Views: 1279

Re: True Altitude

GPS altitude is altitude above a reference plane of a gravitational earth model, not any physical terrain. So it doesn’t correspond with MSL. https://www.esri.com/news/arcuser/0703/geoid1of3.html So while using GPS altitude wouldn’t cause any issues in cruise flight, using GPS altitude near the sur...

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by kalvado
Thu Jan 19, 2023 3:24 am
Forum: Technical/Operations
Topic: 737-800 Single Engine landing
Replies: 15
Views: 1744

Re: 737-800 Single Engine landing

My non-pilot understanding - and hopefully someone would correct me if I am wrong - a first step to handle an engine problem is to reduce power to idle. It still triggers diversion requirement (although not as strict as full shutdown) under the assumption that a problematic engine could still run fo...

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by kalvado
Sun Jan 15, 2023 9:16 pm
Forum: Technical/Operations
Topic: Hybrid Airliner Feasibility
Replies: 47
Views: 2501

Re: Hybrid Airliner Feasibility

So you're saying it's physically impossible to fly with hydrogen on an aircraft because the storage tanks would not have the capacity nor be light enough? P.S. I see no issue with the tank not being connected to the engine. Wing tanks are also tested before they are connected to an engine. Would yo...

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by kalvado
Sun Jan 15, 2023 11:17 am
Forum: Technical/Operations
Topic: Hybrid Airliner Feasibility
Replies: 47
Views: 2501

Re: Hybrid Airliner Feasibility

So? Is a stainless steel dewar 2x the MTOW of the ATR? https://www.airbus.com/en/newsroom/stories/2022-11-the-cold-heart-that-powers-our-zeroe-aircraft So we have a probably serious company, why is long involved in composite tanks, actually delivered some to EASA, saying "demonstrator tank (no...

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by kalvado
Fri Jan 13, 2023 7:39 pm
Forum: Technical/Operations
Topic: Hybrid Airliner Feasibility
Replies: 47
Views: 2501

Re: Hybrid Airliner Feasibility

Where do you get the 2x or more MTOW from? As if that were the case Universal Hydrogen wouldn't be doing something like this as it'd be dead before you even start. https://hydrogen.aero/product/ Do you see any actual numbers on that site? Part numbers. volumes, dry and net weights? Any actual infor...

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by kalvado
Fri Jan 13, 2023 5:26 pm
Forum: Technical/Operations
Topic: Hybrid Airliner Feasibility
Replies: 47
Views: 2501

Re: Hybrid Airliner Feasibility

RJMAZ was saying "Liquid hydrogen has a quarter of the energy per unit of volume compared to jet fuel." But that is a wrong premise as energy content is by mass and not volume. Hydrogen might be low density but if you compress it to a higher density then you will get more mass per volume....

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by kalvado
Fri Jan 13, 2023 2:53 pm
Forum: Technical/Operations
Topic: Hybrid Airliner Feasibility
Replies: 47
Views: 2501

Re: Hybrid Airliner Feasibility

I would beg to differ. Payload of cargo isn't the same as fuel. It is uplifted by volume but all indications on the aircraft are in mass. Your volume will vary with density but the mass stays the same. Therefore it's that what you want to know. Fuel Quantity Indications are in kg or lbs and so is f...

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by kalvado
Fri Jan 13, 2023 12:07 pm
Forum: Technical/Operations
Topic: Hybrid Airliner Feasibility
Replies: 47
Views: 2501

Re: Hybrid Airliner Feasibility

Fuel energy content is per mass and not per volume. You can legitimately do both. Same as payload can be limited by weight (many passenger operations) or by volume (I heard FedEx-UPS run out of space in planes before they hit weight limits) With hydrogen being low density, it needs significant stor...

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by kalvado
Thu Jan 12, 2023 7:31 pm
Forum: Technical/Operations
Topic: Hybrid Airliner Feasibility
Replies: 47
Views: 2501

Re: Hybrid Airliner Feasibility

Metchalus wrote:
Why not? Existing turbines apparently require little modification to run on hydrogen.
Is it because hydrogen is a bit explosive?

I certainly heard that for methane, but I don't think hydrogen would be that simple. Anywhere from metal embitterment to controlled ignition and fun pumping...

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by kalvado
Thu Jan 12, 2023 7:30 pm
Forum: Technical/Operations
Topic: Hybrid Airliner Feasibility
Replies: 47
Views: 2501

Re: Hybrid Airliner Feasibility

The Airbus zeroE pod system won't work. The volume of hydrogen needed for a 1,000nm flight can not fit in the small pod behind the electric motor. Liquid hydrogen has a quarter of the energy per unit of volume compared to jet fuel. A turboprop has the entire wing full of fuel. Now imagine four time...

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by kalvado
Mon Jan 09, 2023 5:50 pm
Forum: Technical/Operations
Topic: Rolls-Royce Completes UltraFan Build
Replies: 26
Views: 4874

Re: Rolls-Royce Completes UltraFan Build

I did not assert that PW invented the geared turbofan. I did not assert that PW was the first to offer a geared turbofan. There is a history of contentious behaviour between RR and PW within the last 15 years over various issues, so I feel that my concern is valid. https://airinsight.com/rolls-lose...

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by kalvado
Sun Jan 08, 2023 11:43 pm
Forum: Technical/Operations
Topic: Hybrid Airliner Feasibility
Replies: 47
Views: 2501

Re: Hybrid Airliner Feasibility

Thirty-five years ago, I was recovering from back surgery, reading Smithsonian’s new magazine “Air & Space”. Article predicting we’d all now be flying intercontinental using Mach 5+ near sub-orbital airliners. See why I’m cynical about these miraculous engineering breakthroughs? And by the way,...

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by kalvado
Sun Jan 08, 2023 11:39 pm
Forum: Technical/Operations
Topic: Hybrid Airliner Feasibility
Replies: 47
Views: 2501

Re: Hybrid Airliner Feasibility

Thirty-five years ago, I was recovering from back surgery, reading Smithsonian’s new magazine “Air & Space”. Article predicting we’d all now be flying intercontinental using Mach 5+ near sub-orbital airliners. See why I’m cynical about these miraculous engineering breakthroughs? You are too blu...

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by kalvado
Sun Jan 08, 2023 8:56 pm
Forum: Technical/Operations
Topic: Hybrid Airliner Feasibility
Replies: 47
Views: 2501

Re: Hybrid Airliner Feasibility

You would have a more defendable case if you start with some real plane and try to get those parameters adjusted to your expectations of new development. Pulling numbers out of thinair isn't too convincing There are no real hybrid aircraft flying yet. But if you type "electric passenger aircra...

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by kalvado
Sun Jan 08, 2023 2:53 pm
Forum: Technical/Operations
Topic: Hybrid Airliner Feasibility
Replies: 47
Views: 2501

Re: Hybrid Airliner Feasibility

200 km/h landing speed isn't significantly lower than jet landings speeds currently. Around 110 knots vs 130-ish. 85% of current speeds, not two-thirds. If your plane cruises at 500km/h, or 270 knots, it would not be far off current jets either. Again, 85-90% of jet cruise speed (in IAS). I said be...

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by kalvado
Sun Jan 08, 2023 9:53 am
Forum: Technical/Operations
Topic: Hybrid Airliner Feasibility
Replies: 47
Views: 2501

Re: Hybrid Airliner Feasibility

200 km/h landing speed isn't significantly lower than jet landings speeds currently. Around 110 knots vs 130-ish. 85% of current speeds, not two-thirds. If your plane cruises at 500km/h, or 270 knots, it would not be far off current jets either. Again, 85-90% of jet cruise speed (in IAS). Either wa...

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by kalvado
Fri Jan 06, 2023 11:06 am
Forum: Technical/Operations
Topic: Hybrid Airliner Feasibility
Replies: 47
Views: 2501

Re: Hybrid Airliner Feasibility

The 787 already is a sort of hybrid aircraft, with electric batteries running systems that formerly utilized bleed air, which adds to the efficiency of the airplane. But engine reliability really isn't the limiting factor with ETOPS, as mentioned. Jet (and turboprop) engines are ridiculously reliab...

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by kalvado
Fri Jan 06, 2023 9:41 am
Forum: Technical/Operations
Topic: Hybrid Airliner Feasibility
Replies: 47
Views: 2501

Re: Hybrid Airliner Feasibility

The 787 already is a sort of hybrid aircraft, with electric batteries running systems that formerly utilized bleed air, which adds to the efficiency of the airplane. But engine reliability really isn't the limiting factor with ETOPS, as mentioned. Jet (and turboprop) engines are ridiculously reliab...

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by kalvado
Tue Jan 03, 2023 12:45 pm
Forum: Technical/Operations
Topic: N1 vs EPR
Replies: 11
Views: 1861

Re: N1 vs EPR

Excellent article - thank you! That explains a lot. And then you have the A350 with its "synthetic" N1 readings to confuse us :) (I believe it averages out the thrust curve so 25% is actually 25% of total thrust, so on a 100K engine it would be 25,000lbs, whereas traditional N1, 25% would...

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by kalvado
Thu Dec 29, 2022 10:41 pm
Forum: Technical/Operations
Topic: Rolls-Royce Completes UltraFan Build
Replies: 26
Views: 4874

Re: Rolls-Royce Completes UltraFan Build

Its exciting to see them moving forward, but as previously mentioned, this is a first step in a very long road. As far as where the greatest technical risk exists, who can say? My guess is that has yet to be identified. Also, you have to assume that PW's lawyers are watching closely. They'd probabl...

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by kalvado
Tue Dec 27, 2022 9:49 am
Forum: Technical/Operations
Topic: Single engine ops with hybrid engines possible?
Replies: 5
Views: 1226

Re: Single engine ops with hybrid engines possible?

I assume hybrid here refers to decoupling of turbine RPM from prop or fan RPM . An electric gearbox, if you will, with ability to cross-feed power via wiring. Possibly vertical stabilizer and rudder may need to have less authority, although unlikely as prop or fan damage, eg by bird strike is still ...

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by kalvado
Wed Dec 07, 2022 5:58 pm
Forum: Technical/Operations
Topic: Question about brake and rudder pedals.
Replies: 25
Views: 3151

Re: Question about brake and rudder pedals.

There's a little art, yes, but it isn't super difficult. The PF will typically have his feet "up" on the rudder pedals for taxi. You can then pivot your foot forward to brake (pressing the top of the pedal to pivot it) and push with your heels to steer. The pedals are interconnected, so w...

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by kalvado
Wed Dec 07, 2022 4:05 pm
Forum: Technical/Operations
Topic: What determines multiple bogey landing gear tilt?
Replies: 11
Views: 1854

Re: What determines multiple bogey landing gear tilt?

Would a nose-down or a nose-up hang impact the ability to grease a landing? In this close-up of a QF A380, there are 2 distinctive impacts (albeit in a very short period of time) when the front wheels of the bogey touches down on the runway, followed very closely by the rear wheels (as it pivots on...

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by kalvado
Sat Dec 03, 2022 11:56 pm
Forum: Technical/Operations
Topic: Fan with electric core - possible?
Replies: 22
Views: 1588

Re: Fan with electric core - possible?

We haven’t had any modern planes spontaneously start fire in flight using fossil fuel. TWA800. And I heard a rumor B-52 exploded at Sawer had a similar issue. TW 800 was a wiring issue. Yes, and several other planes have had ground fires, usually lightning strikes or static discharge due to imprope...

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by kalvado
Sat Dec 03, 2022 11:42 pm
Forum: Technical/Operations
Topic: Fan with electric core - possible?
Replies: 22
Views: 1588

Re: Fan with electric core - possible?

eeightning wrote:
Engine weighs 1/2. Fuel weighs 1/5. That leaves a lot of room for fuel cells and tank insulation.

I believe that pretty much sums the state of the art in hydrogen propulsion over past few decades.

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by kalvado
Sat Dec 03, 2022 11:36 pm
Forum: Technical/Operations
Topic: Fan with electric core - possible?
Replies: 22
Views: 1588

Re: Fan with electric core - possible?

GalaxyFlyer wrote:
We haven’t had any modern planes spontaneously start fire in flight using fossil fuel.


TWA800. And I heard a rumor B-52 exploded at Sawer had a similar issue.

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by kalvado
Sat Dec 03, 2022 10:20 pm
Forum: Technical/Operations
Topic: Fan with electric core - possible?
Replies: 22
Views: 1588

Re: Fan with electric core - possible?

What sort of compact light electric motors are there that could replace the gas turbine core on a commercial airliner? We are talking motors in the 2,000 kw to 50,000 kw range. Is there anything like that at TRL 8? What is the TRL of fuel cells capable of supplying that size motor? I believe fuel c...

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by kalvado
Sat Dec 03, 2022 9:18 pm
Forum: Technical/Operations
Topic: Fan with electric core - possible?
Replies: 22
Views: 1588

Re: Fan with electric core - possible?

Hydrogen as fuel runs into volumetric issues. Presumably we're discussing this in the context of environmental friendliness. Batteries obviously have energy density/volume issues. The Mass issue is even worse. As we know, as such an aircraft won't "lose weight" throughout a flight. As for...

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by kalvado
Sat Dec 03, 2022 11:16 am
Forum: Technical/Operations
Topic: Fan with electric core - possible?
Replies: 22
Views: 1588

Re: Fan with electric core - possible?

So basically there are no hard, technical problems there with such a concept, it's more an issue of fuel volume/range limitations as such, and fuel availability. Thanks for your input. Cheers, Adam There is a concept of "technology readiness level", TRL. It's a 1-10 scale, where 1 means b...

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by kalvado
Fri Dec 02, 2022 8:42 pm
Forum: Technical/Operations
Topic: Fan with electric core - possible?
Replies: 22
Views: 1588

Re: Fan with electric core - possible?

If you can magically store H2 with total energy density per weight and per volume better than that of kerosene, you may start talking drop-in replacements. I'm well aware of lower energy density of H2 liq. https://www.energy.gov/sites/default/files/styles/full_article_width/public/fcto_storage_fuel...

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by kalvado
Fri Dec 02, 2022 8:20 pm
Forum: Technical/Operations
Topic: Fan with electric core - possible?
Replies: 22
Views: 1588

Re: Fan with electric core - possible?

Question is where your design target point is. As far as I understand, fan becomes beneficial at higher speeds, while prop may be more efficient at lower speeds - and for shorter range that is less important. So you loop back at the range of the airplane, which would bring you to fuel storage requir...

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by kalvado
Thu Dec 01, 2022 8:36 pm
Forum: Technical/Operations
Topic: Hawker siddeley trident wing
Replies: 41
Views: 7677

Re: Hawker siddeley trident wing

Dear all, Thank you very much for these insights. I definitely learned something. Now I'd like to ask, how do they design the "automatic pitch down in a developing stall" in a straight wing, e.g. for the Q400 or ATR? A higher pitch angle at the wing root wouldn't change the center of lift...

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by kalvado
Tue Nov 29, 2022 9:57 pm
Forum: Technical/Operations
Topic: Hawker siddeley trident wing
Replies: 41
Views: 7677

Re: Hawker siddeley trident wing

Here is the best I have: This is a very interesting drawing. Take a look at the obvious wing twist from the root to the tip. The angle of attack is significantly higher at the root. Would this design feature induce a stall behavior where the root stalls first, moving the center of lift backwards, t...

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