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.

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.)

Sort of .... the aircraft expanded when at Mach 2, so it grew in length etc. This growth translated itself into the gap that the hat was put in. When it cooled on decel/descent, the gap closed wedging in the hat.

Simples...

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.

Thanks Ex Wok but now I'm even more confused!

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?

This seems to have got lost at the bottom of the last page. Any answers?

http://i1080.photobucket.com/albums/.../Picture16.jpg

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.

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?

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.

No part of the skin will be warmer than the TAT probe, if that helps......

Here's the cockpit temp gauge I photgraphed today:

http://i18.photobucket.com/albums/b132/GZK6NK/TAT1.jpg

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).

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 ?

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.

Indeed, but as a pilot you look after the nose temp... and the rest of the aeroplane will be just fine.

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.

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?

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.

G-AXDN and G-BBDG in the UK have the 3 INS controllers across the front of the pedestal under the primary engineer gauges. I can only suggest that this was dow to the Pilots being the navigators and the engineer being the engineer. Once in Airline service ensuring each crew member has an INS control panel greatly speeded up the checks. Of note 001/002 actually had a navigator in the cockpit behind the Captain, rather than the jump seat.

Standard spec INS systems for that time. Someone may have more information, but they were upgraded over time to having very little memory requiring load from a data card, to having memory for the core routes the aircraft flew in the system permanently, but still only 10 Waypoints could be loaded live at any one time.


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....a bit like how your smart phone can work out your location by cell mast triangulation if it does not have a GPS receiver in it.

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.

Me too, knew most of the Brit. characters, too.

(Only recently shown downundda )

747-400 used GPS to update INS as well as DME when within range. Not a replacement.
At least the ones I was familiar with.

..a bit like the space shuttle evolved to using GPS in addition to the tried and tested systems. Very interesting.

OK, so the skin temperature at the stagnation point will be equal to TAT. This can be taken as the hottest part of the aircraft (behind it, the skin temperature will be less than the TAT).

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?