Hill Helicopters HX50
Joined: Oct 1999
Aviation Qualifications: ATPL
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From: Den Haag
The other problem with larger structures like fuselages is that repairing any damage is nowhere near as simple as with metals. The reduced weight and increased stiffness (in specific planes) is a massive advantage with composites but they are not without their issues.
Joined: Oct 2006
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From: USA
Joined: Mar 2005
Aviation Qualifications: Military
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From: Aus
Originally posted by crab
a definition of a composite structure is using two or more different materials in a structure to create a single structural unit that functions more effectively than individual materials alone.
a definition of a composite structure is using two or more different materials in a structure to create a single structural unit that functions more effectively than individual materials alone.
FAA AC No: 21-26A defines a composite structure as
This advisory circular (AC) provides information about the requirements of Title 14, Code of Federal Regulations (14 CFR) part 2 1, Certification Procedures for Products, Articles, and Parts for quality systems for the manufacture of composite structures. These structures involve fiber-reinforced materials; for example, carbon (graphite), boron, aramid (Kevlar) and glass reinforced polymeric materials. This AC also provides information about essential features of quality systems for composites as mentioned in AC 20-107. Composite Aircraft Structure
Definition - Composite. A material containing two or more distinct materials (fillers, reinforcing materials, and compatible plastic resin) designed to exhibit specific performance properties
Definition - Composite. A material containing two or more distinct materials (fillers, reinforcing materials, and compatible plastic resin) designed to exhibit specific performance properties
Joined: Dec 2001
Posts: 1,471
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From: Here 'n' there!
Originally Posted by [email protected]
Megan, a definition of a composite structure is using two or more different materials in a structure to create a single structural unit that functions more effectively than individual materials alone.
Concorde's elevons and rudders utilized a stainless steel honeycomb core sandwiched between aluminum alloy skins. Ergo, a composite structure
and it was the bonding that started to fail.
Concorde's elevons and rudders utilized a stainless steel honeycomb core sandwiched between aluminum alloy skins. Ergo, a composite structure
and it was the bonding that started to fail.So, simplistically, a honeycomb can be metal sheets with metal filling, metal sheets with composite filling, composite sheets with metal filling or composite sheets with composite filling. Even metal sheets with paper filling back in the day! All are honeycombs - not composites though some honeycombs may contain composites.
Now, you could refer to it as a generic "composite construction" technique but that leads to confusion with the material "composite" hence why you need to be careful and use the specific construction descriptors such as "honeycomb" or "laminate" to avoid confusion.
But I know how you got there! There has always been a trend to use the word "composite" as a "material" and a "construction technique" interchangeably - since the advent of the "plastic" Sea King blade in my experience. I think that's what you have done. However, that is slack (sorry about that!) usage - and hence the confusion! As I mentioned earlier, this is not helped by the fact the word "composite" has several other uses such as composite floorboards which are really laminates.
That's why, in Aviation, the construction is "honeycomb" or "laminate" but the material class is "metal" or "composite" such as GRP or CF etc, or a mix of both. Hope that helps - it is confusing!
Last edited by Hot 'n' High; 31st May 2025 at 09:56.
Joined: Jul 2014
Posts: 446
Likes: 100
From: South East Asia
I see three scenarios:
Scenario 1/ would be nice, but I am afraid that 3/ would be worse than 2/
I am also getting concerned that we have not seen a real test bench for the whole engine, only that one for the starter generator (which is trully an accessory to the whole thing)
in all cases he will sell the hell out of it in a gloriously produced video, you are going to hear that turbine noise spin up, like its the next block buster movie of the summer.
- it works well, its nicely packaged, and meets specification.
- it does not work yet, some problems prevent proper operation... Hill makes a credible explanation has a plan and extend the deadline
- it works, kind off, the gas generator is turning, it looks way unfinished, and we are a miles away from something that can produce reliable power.
Scenario 1/ would be nice, but I am afraid that 3/ would be worse than 2/
I am also getting concerned that we have not seen a real test bench for the whole engine, only that one for the starter generator (which is trully an accessory to the whole thing)
in all cases he will sell the hell out of it in a gloriously produced video, you are going to hear that turbine noise spin up, like its the next block buster movie of the summer.
Joined: Nov 2018
Posts: 240
Likes: 50
From: San Diego, CA
I'm a bit annoyed that they keep putting out videos on things that don't matter, but obviously they have been working on the engine the whole time. But he used to do videos on every bit of incremental progress which makes me fear they are indeed in scenario 2. But *maybe* they're planning some epic reveal of a working section of the engine. I'm certain they're not going to try to run a whole engine if individual parts aren't performing as required, because that would just waste time.
Joined: Apr 2000
Aviation Qualifications: ATP+Mil
Posts: 10,959
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From: EGDC
Hot'n'High - what you say is true but Concorde was composite construction
From New Scientist Magazine
From Iain Barker
It should be noted that there is one significant omission from your “composites as a percentage of total aircraft weight” graph (15 July, p 40).
Aerospatiale/BAC Concorde was the first commercial aircraft to use a composite structure – an aluminium-honeycomb-epoxy composite was manufactured for the elevon and rudder powered control surfaces. Although this pre-dates the more recent “plastic plane” designs of Boeing and Airbus, it does provide a significant case history for the failure modes and the types of in-service fault detection that may be required by a fleet operator.
Concorde experienced a number of composite-structure failures in flight, including multiple delaminations and in some cases the entire loss of large portions of the rudder control surface.
Some failures were traced to water ingress at repair joints on the composite panels, but most failures did not manifest until after several years of normal service with no apparent visual degradation of the external surfaces. As a result, new non-destructive testing techniques (NDT) were developed, including acoustic flaw detection (AFD), water jet “through vibration” ultrasound scans (C-scans) and laser shearography (holographic visual detection).
https://www.newscientist.com/letter/...posite-planes/
Yes, the article is nearly 20 years old but I bow to the scientists....
From New Scientist Magazine
Letter: Composite planes
Published 30 August 2006From Iain Barker
It should be noted that there is one significant omission from your “composites as a percentage of total aircraft weight” graph (15 July, p 40).
Aerospatiale/BAC Concorde was the first commercial aircraft to use a composite structure – an aluminium-honeycomb-epoxy composite was manufactured for the elevon and rudder powered control surfaces. Although this pre-dates the more recent “plastic plane” designs of Boeing and Airbus, it does provide a significant case history for the failure modes and the types of in-service fault detection that may be required by a fleet operator.
Concorde experienced a number of composite-structure failures in flight, including multiple delaminations and in some cases the entire loss of large portions of the rudder control surface.
Some failures were traced to water ingress at repair joints on the composite panels, but most failures did not manifest until after several years of normal service with no apparent visual degradation of the external surfaces. As a result, new non-destructive testing techniques (NDT) were developed, including acoustic flaw detection (AFD), water jet “through vibration” ultrasound scans (C-scans) and laser shearography (holographic visual detection).
Yes, the article is nearly 20 years old but I bow to the scientists....
Joined: Oct 2022
Posts: 16
Likes: 1
From: ireland
I see three scenarios:
Scenario 1/ would be nice, but I am afraid that 3/ would be worse than 2/
I am also getting concerned that we have not seen a real test bench for the whole engine, only that one for the starter generator (which is trully an accessory to the whole thing)
in all cases he will sell the hell out of it in a gloriously produced video, you are going to hear that turbine noise spin up, like its the next block buster movie of the summer.
- it works well, its nicely packaged, and meets specification.
- it does not work yet, some problems prevent proper operation... Hill makes a credible explanation has a plan and extend the deadline
- it works, kind off, the gas generator is turning, it looks way unfinished, and we are a miles away from something that can produce reliable power.
Scenario 1/ would be nice, but I am afraid that 3/ would be worse than 2/
I am also getting concerned that we have not seen a real test bench for the whole engine, only that one for the starter generator (which is trully an accessory to the whole thing)
in all cases he will sell the hell out of it in a gloriously produced video, you are going to hear that turbine noise spin up, like its the next block buster movie of the summer.
Joined: Dec 2001
Posts: 1,471
Likes: 848
From: Here 'n' there!
Originally Posted by [email protected]
Hot'n'High - what you say is true but Concorde was composite construction ......... Yes, the article is nearly 20 years old but I bow to the scientists....
They too can be "slack-Alices" - as they have here!!!!!!! 
After all, they are simply Engineers who prefer nice warm research labs rather than freezing cold and dark hangars ................... and you know what us Engineers are like!!!!!!! Far more balanced and practical!!!!!!!!!!!!!!!!!!!!!! 
Probably try and wind up this thread drift so I'll just add this in closing.They (the Boffins) are correct in that a composite-type material was used in the honeycomb which was then used in a sandwich between alloy skins. After all, the old original metal Sea King blades were the same. Many aircraft flooring structures (were/are) the same. But it was a "honeycomb sandwich" construction. Again, avoid the use of "composite construction" as a technique as it is so loose that it could include plywood ...... which we all know is a laminate construction! "Alice" has an awful lot to answer for!!!!
On Concorde, the bonding between the honeycomb (made out of a composite-type material) and the metal skins failed leading to de-lamination of the honeycomb construction (ie gaps appearing between the metal skin and the honeycomb core). They pick up on that but then become "slack-Alices", tinkers that they are. But they are not composites - they are a "honeycomb sandwich" which, in this case, contained some composite materials within them.
Of course you do get sandwiches that contain both a honeycomb made of composites which is then sandwiched between composite sheets. The first of these were the Beech Starship IIR. But even that isn't a "composite construction" - those parts are a "honeycomb sandwich construction" but, this time, made entirely out of composites ........ and I'll return to this aircraft shortly as you'll be saying "Ah-ha! But the Starship IS a composite aircraft!"!!!!!!!!
But thinking of Concorde-type construction again ............ another example is the Convair B-58 (first flew in Nov, 1956) which had a wing surface consisted of a sandwich structure with Ally skins and a phenolic resin fiberglass cloth honeycomb core. Go the other way, the Mirage F1 horizontal stabilisers were made with boron epoxy skins and an aluminium honeycomb core! There are loads of examples.......
Now, there is a debate as to what constitutes the awarding of a descriptor of what is defined as a "Composite Aircraft" (as opposed to a "Metal Aircraft") and I believe there is some formula regarding %weights of metals and composites used in a design which leads to "it's a composite aircraft" or "it's a metal aircraft" as few aircraft are pure-metal or pure-composite. So, returning to the Beech Starship, this is the rule which makes that a composite aircraft. Clearly, most (all?) modern gliders are "Composite Aircraft" too. BTW, this applies to whole aircraft only ....... not to components there-in used!!!!!!
Anyway, I'll return to lurk-mode here having explored the depths of this particular rabbit warren. Hope it's been of some interest - or helped people with bad insomnia!!!! Apologies to the Mods for this dive off-track - I blame "Alice"!!!!!!!!!!
Last edited by Hot 'n' High; 2nd June 2025 at 14:43.
Joined: Jun 2006
Posts: 1,022
Likes: 2
From: In the air with luck
I'm a bit annoyed that they keep putting out videos on things that don't matter, but obviously they have been working on the engine the whole time. But he used to do videos on every bit of incremental progress which makes me fear they are indeed in scenario 2. But *maybe* they're planning some epic reveal of a working section of the engine. I'm certain they're not going to try to run a whole engine if individual parts aren't performing as required, because that would just waste time.
I feel that as the same as you, not keen on the 2 talking heads either
Joined: Oct 2022
Posts: 16
Likes: 1
From: ireland
I'm pretty sure they're quiet because there is no progress. I'll bet there will be a big announcement to say its delayed but its a good thing and itll definitely be working by Christmas..... until Christmas come around!
Joined: Dec 2017
Aviation Qualifications: SLF
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From: Yakima
Guest
Joined: Jul 2017
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This is certainly what I am hearing on the grapevine
