gordonroxburgh
3rd Jun 2001, 02:24
These have been a couple of posts about Concorde's flight profile lately, so I though I would post this article By John Wiley that was published in July 2000's Business & Commercial Aviation magazine (before the Air France Accident)
The gig is that the author wanted to fly Concorde, BA said no (surprisingly!!!!..), but he could fly the sim with Mike Bannister.
Here it is................
In a typical shoot-for-the-moon request, I have asked to fly this unique airplane although it is three decades old. Only 20 were built (two prototypes, two pre-production aircraft and 16 production aircraft), although initially, there were plans for 74 of these amazing machines.
American, Eastern, TWA and United each wanted six. Braniff, Continental and Lufthansa said they each would take three aircraft. BOAC (forerunner of British Airways), Air France and Pan American wanted eight. Other carriers included Air Canada (4), Air India (2), Japan Airlines (3), Middle East Airlines (2), Qantas (4) and Sabena (2). Flush with orders, manufacturers said they could scale up production to build 150 airplanes but when the time came to confirm the orders, Pan American balked. Almost immediately, the other airlines followed suit and in the end, only two airlines took delivery. Only Air France and British Airways operate the 2.0 Mach Concorde.
My request to fly Concorde was, to use the jargon, a "non-starter." The backup request to ride on a training sortie also floundered quickly. But our request to fly the simulator took wing and I am headed for Bristol and one of the only two Concorde simulators in the world.
Systems
The focus of this article is Concorde's flying characteristics and systems. Even though, the airplane is more than 30 years old, however, many of Concorde's systems are unique and to omit all systems discussion would relegate the article to "I pushed," "I pulled" and "fuel flow was . . . ." Concorde is more than just stick and rudder, and to understand that, we have to touch on its systems.
The Wing
The big ogival wing is unique as is the fact that Concorde has no ailerons, speed brakes, spoilers or leading edge flaps/slats. Concorde has six elevons, grouped in three pairs, for pitch and roll. Concorde also has no trailing edge flaps, but the elevons droop on takeoff and for landing to create increased wing camber. The six elevons are hydraulically powered and electrically controlled -- as in "fly by wire." (Although many are convinced the Airbus A320 family was the first fly-by-wire airliner, Concorde pioneered the concept a decade earlier.) According to Mike Bannister, British Airways' Concorde chief pilot, there were even studies to use a side-stick controller in Concorde but, he noted, "Concorde was making so many large steps, this was one that would have to wait." Concorde has two electric channels to signal the flight controls and there is a mechanical backup.
The Fuel System
Concorde's multi-function fuel system also is complex, and in comparison, the 727's flight engineer panel is a piece of cake. One Concorde flight engineer described the fuel system as ". . . typically British. There are 13 fuel tanks, numbered one through eleven."
Fuel tanks 1, 2, 3 and 4 are engine feed tanks. Tanks 5, 6, 7, 7a, 8 and 8a are transfer tanks that flow into the engine feed tanks. The forward tanks, number 9 and 10, and the aft tank, number 11, are trim tanks used to move Concorde's c.g. fore and aft during cruise. Total fuel is 95,430 kilograms, or 209,946 pounds (approximately 26,400 gallons).
Concorde has four refueling points, two in front of each main landing gear. The automatic refueling system first puts fuel in the forward-most tank, tank 9, to ensure Concorde does not squat on its tail. Tank 11, the aft most tank is filled last.
But the fuel is used for other purposes besides feeding the thirsty Rolls-Royce Olympus engines. It also is used as a heat sink to cool hydraulic fluid and air passing through the air conditioning heat exchangers.
In flight, the flight engineer also uses the fuel to shift Concorde's c.g. as it accelerates. Shifting the c.g. aft (from 51 to 52 percent Mean Aerodynamic Chord for takeoff to 58 percent at 2.0 Mach) keeps the center of lift relatively stationary and the elevons relatively flush. This is extremely important as any control deflection creates drag and drag equals increased fuel consumption. During deceleration, for landing or as the result of an engine failure, fuel must be shifted forward.
Transfers are closely coordinated between the flight engineer and the pilot to maintain optimum controllability of the aircraft. With an outside temperature higher than normal, fuel can transfer aft faster than the airplane can accelerate. Likewise, in colder than normal air, Concorde will accelerate faster than fuel can be transferred aft. In either case, the fuel transfer is not a simple task of just opening a valve and turning on pumps.
The Hydraulics
Concorde has three 4,000-psi hydraulic systems. Like the Airbus, the main systems are color coded. The main systems are blue (engine pumps 3 and 4) and green (engine pumps 1 and 2) with yellow (engine pumps 2 and 4) as the standby system. Hydraulics power the elevons, intakes, landing gear, visor and drooping nose (the nose droops to five degrees for takeoff and 12 degrees for landing. Only the nose droops. The cockpit does not move. Instead, a glass shield -- or visor -- comes down to close the gap between the cockpit windows and the nose. The visor is down for takeoff and landing). Two electric hydraulic pumps are available for ground use and a ram air turbine can power one green pump and one yellow pump in an emergency.
The Engines
The engines are Rolls-Royce/SNECMA Olympus 593 Mark 610 turbojets. Turbojets -- not high-bypass fans. High-bypass fans offer good fuel flows in the lower atmosphere but they tucker out at high altitude/high speed. Worse yet, they are heavier than turbojets. Turbojets may seem to be relics of the past but at 2.0 Mach, the turbojet is the right engine. With afterburner, or reheat to use the British term, each of four engines produces 38,050 pounds of thrust on takeoff. In 2.0 Mach cruise, it is another story -- but more about that later.
To quickly hit the other systems, there are four gear lights. Nose gear, two main gear and a retractable tail bumper. The electrical power comes from four 60kVA engine-driven generators with four 150-amp transformer-rectifiers and two 25-amp/hour batteries. Maximum cabin pressure differential is 10.7 psi, which gives a 6,000-foot cabin at 60,000 feet. This lower cabin altitude and, obviously shorter times in flight, contributes to less fatigue compared to airliners that trudge along five miles lower than Concorde and have cabin altitudes of about 8,000 feet.
The Briefing
I meet British Airways' Bannister in Bristol. He has just completed his checkride, and with an accomplished flare and four colored markers, he begins a quick, but detailed, briefing on how to fly Concorde. As I furiously scribble notes, I mentally note that normal check out on Concorde is six months, including six weeks of "chalk and talk" classroom sessions. There is no computer-based training on Concorde and the classes for pilots and flight engineers are small and intense, with most of the instruction given one-on-one.
After the ground school, pilots complete 19 four-hour simulator sessions. The first two simulator rides cover normal handling and the other 17 include emergencies and abnormals. After a simulator checkride, aviators then get a minimum of 14 landings in the airplane. Completing this, they fly the line for two months with a check airman before receiving a line check. Four months after the line check, the Concorde pilot returns for additional training including lightweight takeoffs. I am getting the "short course." The "very short course."
During the briefing, Bannister pens in some impressive numbers. Takeoff weight will be 185,000 kilograms (407,000 pounds). The V speeds are V1, 166 knots; Vr, 197 knots; and V2, 219 knots or 11 knots below the maximum tire speed on many jets. Bannister frequently refers to angle of attack along with airspeed for a given flight regime. After filling up and erasing the board maybe four or five times, we head for the simulator. I think, "Concorde pilot in 90 minutes? This is going to be real interesting."
In the Sim
As one would imagine, Concorde's cockpit is not exactly spacious. It is more like a small nest for three. And like a small nest, before a pilot can move, the flight engineer must move. I nest first in the left seat. The seat is electrically powered with a manual backup and adjustable armrests. Rudder pedals adjust fore and aft. I make an arm sweep of the cockpit and find most things within easy reach. I note the overhead panel is not really overhead but more side-head since it sits about two inches above my eye level. The panel's ends are thickly paneled, no doubt to prevent painful, eye-closing encounters. I look up and realize the area above my head is not a flat panel but rather a neat little arch for my noggin. No wasted space. As I said, Concorde's cockpit is a cozy place.
The ram's horn control column fits neatly in my hands. On the outboard horn is a pitch trim switch and on top of the inboard horn is a small wheel that controls a pitch bug on the attitude indicator. On takeoff, the attitude indicator is clean -- no flight director. Just the pitch bug, which, on takeoff, is set to a calculated pitch termed "theta 2." For our weight and conditions, "theta 2" is 13.5 degrees.
On engine start I am surprised at the how quickly the Olympus engines come to life and at the remarkably low idle temperatures (about 210°C to 220°C). Fuel flow also seems low at 1,100 until I see the "kg" decal. I do the quick math (2.2 x 1,100 x 4). Almost 10,000 pounds/hour in idle? Long taxi delays could easily be a problem.
Systems online, we taxi to the active. Simulators are notoriously bad devices for taxiing but this one seems quite real. No problems with brakes but I have to remember the cockpit is 38 feet in front of the nose gear and 97 feet in front of the main gear. I go well beyond the intersecting taxiways before I begin my turns. Lined up for takeoff, Bannister quickly reviews the takeoff profile.
All takeoffs use reheat for the best noise footprint. The takeoff profile is calculated on gross weight, temperature and the specific runway and is timed. Our takeoff profile is 1:23, which we enter in a countdown clock. When cleared for takeoff, I count, "Three, two, one, NOW!" and upon the command, "NOW", I punch the clock and slam the throttles wide open. "Slam" as in moving the throttles from idle to full forward in about one second. The engines use a fuel control unit that accelerates the engine to maximum thrust, and for it to operate properly, one does not gingerly ease the throttles open. Release the brakes, countdown and BAM!
Acceleration is quick and out of the corner of my eye, I see four green lights illuminate, which indicates we have four burners. I also note engine fuel flows at 24.9, 25.1, 25.0 and 24.9 for a rough total of 100. This fuel burn will deplete our 95,000 kilograms in less than an hour. Doing the math, I calculate we are burning 220,000 pounds/hour.
Bannister calls "airspeed building" and 0:21 after the throttle slam, we are at "100 knots." Speed builds very quickly now. At 0:31 we hurtle by V1 and at 0:40 I rotate at 195 knots.
I try to park my pitch right on "theta 2," 13.5 degrees. The gear comes up quickly and about 0:47 after brake release, we are climbing at V2 (217 knots) and accelerating. Speed continues to build and in less than one minute I am at 240 knots and pulling up the nose to 18 degrees to maintain 250 knots. We approach the end of timing and I hear, "Three, two, one, noise!" With that, the flight engineer cancels the burners and pulls the engines back for a noise abatement profile. With the thrust reduction, I drop the nose to 13 degrees and continue climbing at 250 knots. The VSI seems a sedate 1,500 fpm.
At this speed, there is a constant burble. Bannister explains the burble comes from the vortex lift. He smiles and advises that we are well on the backside of the drag curve and for this weight, minimum drag speed is 300 knots. The burble disappears when Concorde picks up speed.
We are cleared to accelerate so I lower the nose to eight degrees pitch. Bannister gives me a flight director and then repositions a small knob above the landing gear selector. In less than four seconds, the shield comes up and the noise level falls off noticeably.
We are quickly at 0.70 Mach when the flight engineer begins moving fuel aft. As Concorde comes into its element, performance improves. No more burble and the rate of climb increases to 4,000 fpm. Out of 16,500 feet, we are accelerating to the barber pole (Vmo) and indicating 395 knots/0.80 Mach. Bannister points out a small and unusual Mach meter by my left leg. It has brackets to show minimum and maximum Mach for a given altitude and configuration. (Later, when we are indicating about 1.6 Mach, I check this meter to find the minimum speed for this altitude, weight and c.g. is 1.10 Mach.)
Out of 25,000 feet we are climbing 3,000 fpm and indicating 393knots/0.91Mach. We level for a minute to demonstrate Concorde's ability to fly with a jammed control. Should this happen, the pilot can push a small button in the center of the ram's horn controls and fly the airplane by using small pressures. Bannister estimates the pressures to be around 10 to 15 pounds but this force is read by a strain gauge and sensors that transmit the input to the elevons -- basically, a backup fly-by-wire system.
We go back into a normal mode and I try to tuck the airspeed needle into the Vmo needle, which is another little oddity. The Vmo needle is notched and for maximum performance, the pilot tucks the indicated airspeed needle right into that notch. As you can imagine, when hand flying at Vmo, it is easy to drop pitch a half degree and get the overspeed horn. As we climb, I get honked at occasionally. I think, "Better a honk than a stall warning!" (Although there is no requirement to use the autopilot on Concorde and some pilots have been known to hand-fly the entire route from London to New York, for best fuel economy, "George" flies.)
There is no change in handling when the Mach meter changes from 0.99 to 1.0 except for some slight jumps on the VSI and altimeter. Out of FL 330 we are indicating 410 knots/1.10 Mach. Bannister points out Concorde's angle-of-attack indicator. We are now down to 4.5 units angle of attack and Bannister says that anything above seven units creates the rumble. Later, in the traffic pattern, the rumble returns and I find the angle-of-attack indicator is used quite a bit for landing Concorde.
We reach a critical point at 1.3 Mach. This is where digitally controlled ramps within the engine intake ducts start to drop down. These ramps create a shock wave that slows the air within the intake. At 1.7 Mach, the ramps are so efficient that we pull the engine out of afterburner and Concorde continues to accelerate. Best of all, fuel flow is cut almost in half. According to Bannister, when cruising at 2.0 Mach, the intakes and exhaust nozzles are producing most of the thrust. The Olympus engines, with the thundering 38,050 pounds of thrust on takeoff, are now producing only nine percent of the total thrust. At 2.0 Mach, the ramps have dropped to almost 45 degrees and the air within the duct slows from approximately 1,350 mph at 2.0 Mach to around 500 mph before it enters the engine. All this wizardry happens in about 11 feet of duct.
At 2.0 Mach I complete a few turns up to 30 degrees bank. Nothing special in the turns but I have to be extremely attentive to pitch as each degree of pitch is a 2,000 fpm climb or descent. In this short tour, I find no unpleasant surprises in Concorde's handling, but wonder if there aren't some bad manners somewhere.
I ask Bannister to show me the ugly stuff, the things that conjure up pilots' nightmares. I am thinking of an immediate seizure of two engines on one side. I remembered reading this event caused the inflight breakup of a Convair B-58 Hustler. Bannister readily agrees to demonstrate this, but first he briefs me on how Concorde will react.
Bannister explains, "Concorde yaws into the dead engines just like a normal airplane but it rolls away from the dead engines. When the engines fail, they can no longer take the airflow so the digitally controlled intakes open doors and the air is dumped out the bottom. This produces the roll in the opposite direction."
To prove his point, Bannister abruptly yanks engines one and two to idle. Concorde yaws left. Concorde rolls right. With a small input on the ram's horn, I counter the roll and that basically ends the excitement for me. Of course, the flight engineer has to scramble to move fuel forward as we slow but the handling is not even a bad dream, much less a nightmare.
Our last demonstration at cruise shows Concorde will not tolerate abuse. Obviously, to counter a dual engine failure at 2.0 Mach, the airplane needs a powerful rudder. However, heavy feet and a powerful rudder are not a good combination at 2.00 Mach. Bannister suggests I try to push the rudder to the floor. But the aircraft has a form of envelop protection that limits my input .
Next, Bannister freezes the simulator, sheds tons of weight and reestablishes the simulator on the runway at Shannon for our pattern work. Our weight is now down to a mere 125,000 kilograms (275,000 pounds) to simulate lightweight, high-performance handling. On takeoff, I pitch up to a "theta 2" of 18 degrees and accelerate to 250 knots. On downwind at 1,500 feet agl, I notice the aerodynamic rumble is back. It is with us the entire time we are in the pattern. I fly seven degrees of pitch and constantly keep referring back to the angle-of-attack indicator for guidance. To fly final, I should note the angle of attack and subtract three degrees for the proper glidepath.
Abeam the touchdown point I am at 210 knots and 8.5 degrees pitch. Base leg is 190 knots and Vref is 162 knots. I twirl my pitch button up to 13 degrees for my level flight attitude reference. Bannister breaks down the pattern by saying, "Always use the autothrottle and stay on instruments down to 500 feet agl. At 500 feet, one glance out for two glances in the cockpit. At 200 feet, one glance in for each glance out. Keep aiming for the 'piano keys' on the runway. At 100 feet, one glance in for two glances outside. At 50 feet, disengage the autothrottles and at 20 feet check the descent by raising the nose one-degree. This will let the airplane ease through ground effect. Once on the runway, keep pulling aft on the column to keep the nose from coming down rapidly." I have to smile. I am learning "How to Land Concorde" in about 60 seconds. But Bannister is good and his techniques right on. I try to do as instructed and although I land long a few times, the landings seem acceptable -- at least I don't break the sim.
To finish the simulator ride, we accomplish a few V1 engine failures. I am surprised that Concorde takes less effort to keep on centerline than some jets I have flown. Compared to the 737-300 or one of my earlier favorites, the Lear 23, keeping Concorde on centerline is a piece of cake. Flying a three-engine approach also poses no significant challenge with Bannister's coaching. All too quickly, we have done 2.5 hours in the simulator and it is time to "drop the box." Bannister hits the button and the simulator session is over.
Summary
One thinks of many things after a short, intense session in Concorde's simulator. To the video generation that has grown up with EFIS and glass, the cockpit must look a bit arcane -- full of myriad switches and round dials. (Concorde even has a round dial to monitor radiation, the only airplane in airline service with such a device. When the crews flying into Dulles noted some spikes on the radiation meter during the arrivals and departures in Washington, they inquired about the source. They were told to just fly and forget the radiation spikes.) There is no consideration to upgrade to glass, and when asked about upgrades such as GPS, the line captain grinned and told me, "Triple INS is quite sufficient for a short three-hour flight across the Atlantic." He had a point, especially after engineers had a heck of a time just figuring out how to attach a new antenna to meet the FAA's TCAS requirements.
Back in the hotel, I review my notes and actually feel a bit confident about the simulator session. I didn't crash it and with Bannister's cribbing, I was able to land Concorde within the runway confines.
Concorde's handling is good and the controls are well harmonized in pitch and roll but they are not exactly light. With such agile airplanes as the Falcon 2000 at one end and the Boeing 727 at the other end, Concorde easily leans toward the 727 end of the scale. I think of repeated emphasis on pitch. Pitch. Pitch. Pitch. To fly Concorde, you have to be constantly aware of pitch.
Concorde is obviously unique. There are fewer Concorde pilots, past and present, than astronauts and it is still the world's only airplane that routinely cruises at 2.0 Mach. But how difficult is Concorde to fly? One simulator session may not be the best measure for this answer, but let's just say it takes a lot of commitment to fly Concorde. The six-month initial training program is no small challenge. But stick and rudder skills? I believe Concorde requires strong stick and rudder skills, but more, it requires good head work and a lot of attention to pitch when on final. Lots.