Concorde question

[paulross]

Concorde Thread Re-mixed

I have just rebuilt my website that re-organises this popular Concorde thread by subject, it is here: https://paulross.github.io/pprune-th...rde/index.html

Main Changes:

• Added pages of posts that link to popular sites such as YouTube: https://paulross.github.io/pprune-th...external_links (97 posts).
• Added pages of posts that contain images (useful for quickly finding that chart, photo or diagram): https://paulross.github.io/pprune-th...E-IMAGES0.html (122 posts).
• Added a link to a post that links to a site with all the Concorde manuals: Concorde question
• Added subjects: "BAC221", "HP115", "Radiation Exposure", "Brian Trubshaw", "Andre Turcat", "John Cochrane", "Fuel Saving Landing", "Manuals", "Marilake Display", "Fuel Burn", "Area Rule", "Eclipse Chasing", "Skin Temperature", "Static Ports" and expanded existing subjects.

Over 2000 posts are organised into 196 subjects.
Around 30% of the posts on the thread are excluded because I can't pick up a subject from that post so please contact me if you feel that you contribution has been excluded.

The project is here: https://github.com/paulross/pprune-threads
Issues can be raised here: https://github.com/paulross/pprune-threads/issues or PM me.

[Bug]

Paul
Monumental effort. So great that you have preserved this.
I hope the place your site and the info is stored on endures indefinitely, if that is not too much to hope for.
i really see this as an historic record that will be used by future historians, as maybe Concorde will never be repeated.
Seems like the 60's was the high water mark of aviation.

[paulross]

Thanks Bug
I have put everything on my public GitHub account so, thanks to them, it has a reasonable chance of lasting indefinitely.
Let me see if I can get the WayBack Machine (the Internet Archive) to archive the site.

[EDHL]

I have some questions on engine control that I hope haven't been covered yet (I'm only about 70 pages in).

First, let me make sure that I've got the general principles right:

• Throttle lever angle (TLA) commands a desired N2, such that a given TLA always corresponds to the same N2. The throttle control unit controls the throttle valve to achieve the desired N2.
• The current engine control schedule determines the N1 that should be achieved for a given N2. The TCU controls the primary nozzle to achieve the desired N1.

Is this correct so far?

Now on to my questions:

• Can someone give me a technical reference that plots the exact numerical relationship between TLA and N2? I've found a noise abatement table, which gives me useful values between TLAs of 11.2 and 27, but I can't find values outside that range. The N2 for a TLA of 34 would be of particular interest to me, as this TLA is used in the transonic deceleration below Mach 1.6.
• Similarly, I'm looking for a reference on the relationship between N2 and N1 for each of the engine control schedules. There's a graph on page 18.02.10 of the Concorde Flying Manual volume 1 that shows this relationship, but there is no numerical scale on the axis. Can someone point me to a similar graph but with numbers on the axes?

The reason I'm asking is because I'd like to tweak the relevant behaviour of the Colimata Concorde addon for the X-Plane PC flight simulator.

I suspect that, these days, the people working on the Brooklands sim may be the most likely to have this kind of information. Are there people from that team on this forum, or does someone here know someone on the team?

(By the way, I wanted to include some links to the documentation above, but I don't have enough posts yet.)

[CliveL]

It's way out of date but you will get some idea from Fig 5 of Olympus 593 Control System by C E G Payne published in Aircraft Engineering April 1967

[EDHL]

Originally Posted by CliveL

It's way out of date but you will get some idea from Fig 5 of Olympus 593 Control System by C E G Payne published in Aircraft Engineering April 1967

Thanks, that's very helpful! It hadn't occurred to me to go looking in the academic literature.

I see from the paper that TLA does not correspond purely to an N2 demand, as I had previously believed. TLA does appear to control N2 at higher power settings, but at lower power settings, it instead more directly controls fuel flow.

To check my understanding, I'll summarize what I think is going on.

As I understand it, a given TLA produces two demands: A direct fuel flow demand and an N2 demand. The N2 demand, in turn, feeds into a controller that compares the demanded N2 against actual N2 and from this produces its own fuel flow demand. The two fuel flow demands - the one derived directly from TLA and the one coming from the N2 controller - are then compared, and whichever of them is higher is used to drive the throttle.

The result of this is that there is a changeover between TLA producing a direct fuel flow demand (at lower TLA) and an N2 demand (at higher TLA), and this changeover can be seen in Figure 5 as a "knee" in the fuel flow curve.

Moreover, the specific TLA value at which the changeover happens depends on altitude. For higher altitudes, the changeover happens later, i.e. at a higher TLA. I presume this is because the fuel flow required for a given N2 reduces with altitude, so the range of TLAs at which the direct fuel flow demand dominates becomes larger with altitude.

Do I have all of this correct?

Some followup questions:

• The engine appears to reach maximum power at around 90% of the throttle lever's range, with no further change in engine parameters beyond this point. I imagine the purpose of this deadband is to account for tolerances in the engine control and ensure the engine achieves maximum power when the throttle is pushed all the way forward?
• I don't see any mention in the article of the engine control schedules (lo, mid, hi, flyover). I assume these were only introduced later in the development programme? Do you have a sense which engine control schedule the graphs in Figure 5 would most closely correspond to?