Concorde question
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1) Effectively it was (not the skin, but the TAT probe. The highest temp rise would be at the stagnation point so one can be confident that TAT is a realistic answer for max skin temp).
2) AFAIK pretty standard:
Q from pitots
S from statics
T from temp probe
Modified by ADC for position error. It's possible that ADC used beta inputs and I'm sure it used alpha inputs to achieve this.
2) AFAIK pretty standard:
Q from pitots
S from statics
T from temp probe
Modified by ADC for position error. It's possible that ADC used beta inputs and I'm sure it used alpha inputs to achieve this.
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Possibly daft question about expansion joints
The exhibit at the Seattle Museum of Flight (Alpha Golf, I think) has the story of the flight engineer who placed his cap in what's called "the expansion joint."
But I can't figure out how the "expansion joint" got itself closed when the airplane was cold, and open when the airplane was hot. Seems backwards to me.
In my mind, the cool airplane has smaller parts, and therefore larger gaps in the joints.
What am I missing?
(I shudder to ask this question, since I have the tingle on the back of my neck that usually tells me I'm missing something simple.)
But I can't figure out how the "expansion joint" got itself closed when the airplane was cold, and open when the airplane was hot. Seems backwards to me.
In my mind, the cool airplane has smaller parts, and therefore larger gaps in the joints.
What am I missing?
(I shudder to ask this question, since I have the tingle on the back of my neck that usually tells me I'm missing something simple.)
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In my mind, the cool airplane has smaller parts, and therefore larger gaps in the joints.
Simples...
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Yep that's it.
Imagine it this way - the outside of the hull is hot and expands. The floor and other interior components, however, are about 100 degs cooler and so not subject to the same expansion. In a very simplified description, if you imagine the floor on rollers but attached at one end then you'll see a gap at the other end when the exterior hull stretches. That's the effect you see when the expansion gap appears aft of the FE's panel in supersonic flight. (The floor is, by the way, not just sitting on rollers.....)
Electrical looms had a little sag between fixed points if they were attached to 'expanding' parts of the airframe.
And so on.
It's amazing there was ever any hydraulic fluid left on board if you consider the stresses and aggro involved in routing the pipes and hoses.
Imagine it this way - the outside of the hull is hot and expands. The floor and other interior components, however, are about 100 degs cooler and so not subject to the same expansion. In a very simplified description, if you imagine the floor on rollers but attached at one end then you'll see a gap at the other end when the exterior hull stretches. That's the effect you see when the expansion gap appears aft of the FE's panel in supersonic flight. (The floor is, by the way, not just sitting on rollers.....)
Electrical looms had a little sag between fixed points if they were attached to 'expanding' parts of the airframe.
And so on.
It's amazing there was ever any hydraulic fluid left on board if you consider the stresses and aggro involved in routing the pipes and hoses.
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1) Effectively it was (not the skin, but the TAT probe. The highest temp rise would be at the stagnation point so one can be confident that TAT is a realistic answer for max skin temp).
2) AFAIK pretty standard:
Q from pitots
S from statics
T from temp probe
Modified by ADC for position error. It's possible that ADC used beta inputs and I'm sure it used alpha inputs to achieve this.
2) AFAIK pretty standard:
Q from pitots
S from statics
T from temp probe
Modified by ADC for position error. It's possible that ADC used beta inputs and I'm sure it used alpha inputs to achieve this.
1) So there is a direct temp reading, from the TAT probe. But where is TAT probe? Is it in the needle nose probe that also measures pitot/static for the intake computers? And how many TAT sensors are there (failure of a single one if that's all there is would not be good)?
2) Mach comes from dynamic pressure (pitots), from static ports, and from temp. But what temp? OAT perhaps?
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Originally Posted by Shanewhite
Several times I've seen mention of the cockpit crown mods. What were these, and what was the reason for them? Were they applied to all the airframes?
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SSD:- this answers your question on where the TAT probes were located. Strictly, you don't need temperature to calculate Mach as it is independent of temperature when expressed in EAS (or CAS) terms.
Shane:
The "crown modifications" were external straps to be applied to the upper part of the fuselage to extend its life in those areas which had been designed to safe life concepts - basically the Aerospatiale bits since BAe designed their bits according to damage tolerance rules. It wasn't a small job, but I'm afraid I can't tell you how many aircraft were modified.
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Thanks Clive but I'm still going around in circles. Those sensors measure OAT do they not? They are spaced out from the (hot) skin to do that, presumably.
Can you confirm just how that tells the crew the skin temp? Are there no direct-reading temp sensors on or under the nose skin or in the probe?
Can you confirm just how that tells the crew the skin temp? Are there no direct-reading temp sensors on or under the nose skin or in the probe?
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So far as I know, they were standard TAT measurement instruments, so they gave Total Air Temperature directly.
There was, so far as I recall, no measure of skin temperature - the aircraft limit (Tmo) was simply based on a measured TAT of 400 degK. The implied limits on skin temperature at various points were built into the design cases.
There was, so far as I recall, no measure of skin temperature - the aircraft limit (Tmo) was simply based on a measured TAT of 400 degK. The implied limits on skin temperature at various points were built into the design cases.
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Here's the cockpit temp gauge I photgraphed today:
So the TAT probe provides TAT (obviously) which effectively is skin temp (as evidenced by the TMO legend of 127C just below the TAT window?).
(TAT being static air temp plus the temp due adiabatic heating).
So the TAT probe provides TAT (obviously) which effectively is skin temp (as evidenced by the TMO legend of 127C just below the TAT window?).
(TAT being static air temp plus the temp due adiabatic heating).
Last edited by Shaggy Sheep Driver; 28th Apr 2012 at 20:14.
Thread Starter
For some reason I seem to remember a picture of a Concorde Cockpit with four INS sets side by side, was this ever the case or just my imagination ?
Also, were the INS installed specially developed for Concorde or were they the same as fitted in the B747 for example.
Finally was GPS updating to the INS position ever developed and installed ?
Also, were the INS installed specially developed for Concorde or were they the same as fitted in the B747 for example.
Finally was GPS updating to the INS position ever developed and installed ?
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http://i1080.photobucket.com/albums/.../SkinTemps.jpg
Not exactly skin temperature, just the maximum temperature on the nose. The rest of the aircraft was cooler.
Not exactly skin temperature, just the maximum temperature on the nose. The rest of the aircraft was cooler.
So TAT is skin temp at the probes, which are rearward of the hottest skin according to that diagram. Was there a 'compensation' built into the TAT readout to account for the relatively rearward position of the TAT probes?
And.. How was static temp readout derived?
Sorry to keep asking, but I really want to understand this!
Thanks.
Last edited by Shaggy Sheep Driver; 28th Apr 2012 at 21:45.
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So TAT is skin temp at the probes, which are rearward of the hottest skin according to that diagram. Was there a 'compensation' built into the TAT readout to account for the relatively rearward position of the TAT probes?
And.. How was static temp readout derived?
And.. How was static temp readout derived?
They are mounted off the skin and in freestream, so they measure the same temperature as would a probe on the nose.
Somewhere near the nose (not exactly on it, as the aircraft flies with a small AoA) there will be a 'stagnation' streamline where the oncoming air is brought to rest. At this point the skin temperature will be equal to the stagnation temperature (TAT). Behind that it gets more complicated! The skin temperature would depend on SAT, local Mach No, local skin friction coefficient (Mach and Re dependent, so varies with distance from nose), amount of heat radiated into space (paint colour!) and the amount of structure available to conduct heat away from the skin into the fuel (so roughly varying with thickness/chord and fuel distribution perhaps?
Static temperature and total temperature are related by a simple expression:
TAT = SAT *(1+0.2m^2) all in deg K
So in the troposphere at ISA +5 and Mach 2, SAT = 222 and TAT = 400.
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For some reason I seem to remember a picture of a Concorde Cockpit with four INS sets side by side, was this ever the case or just my imagination ?
Also, were the INS installed specially developed for Concorde or were they the same as fitted in the B747 for example.
Finally was GPS updating to the INS position ever developed and installed ?
Very relevant for the current time: it was a similar INS system that was hashed into the Vulcan to allow it to find the falklands for the blackbuck raids.
Just watched the documentary on the life and demise of the Concorde. The pride of everyone who was involved is clearly evident.
It's brought me to tears.
It's brought me to tears.
(Only recently shown downundda )
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GPS would been a complete replacement for an INS. The clever thing the INS system could do was use DME updating to refine their position when in range of a ground station.
At least the ones I was familiar with.
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Er - no, the TAT probes measure just what they say Total Air Temperature.
They are mounted off the skin and in freestream, so they measure the same temperature as would a probe on the nose.
Somewhere near the nose (not exactly on it, as the aircraft flies with a small AoA) there will be a 'stagnation' streamline where the oncoming air is brought to rest. At this point the skin temperature will be equal to the stagnation temperature (TAT). Behind that it gets more complicated! The skin temperature would depend on SAT, local Mach No, local skin friction coefficient (Mach and Re dependent, so varies with distance from nose), amount of heat radiated into space (paint colour!) and the amount of structure available to conduct heat away from the skin into the fuel (so roughly varying with thickness/chord and fuel distribution perhaps?
They are mounted off the skin and in freestream, so they measure the same temperature as would a probe on the nose.
Somewhere near the nose (not exactly on it, as the aircraft flies with a small AoA) there will be a 'stagnation' streamline where the oncoming air is brought to rest. At this point the skin temperature will be equal to the stagnation temperature (TAT). Behind that it gets more complicated! The skin temperature would depend on SAT, local Mach No, local skin friction coefficient (Mach and Re dependent, so varies with distance from nose), amount of heat radiated into space (paint colour!) and the amount of structure available to conduct heat away from the skin into the fuel (so roughly varying with thickness/chord and fuel distribution perhaps?
The temperature shown in the top window of the flight deck gauge is TAT, with the legend 'TMO 128C' beneath it. So the aircraft was flown with reference to TAT, and provided TAT was no greater than 128C then the skin rearward of the stagnation point would be <128C?