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Water injection?

Old 19th Nov 2022, 21:36
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I flew the KC 135 from 1974 to 1988. The A model carried 2000 lbs of demineralized water that lasted about 2 minutes on takeoff which usually got us up to 500 feet or so if heavy and 2000 feet if light. It could be used down to 40 degrees F. It gave a little over 1000 lbs of thrust per engine which is needed when the engine only puts out a little over 12,000 lbs for a 297,000 lb airplane. The R model's CFM 56 put out 22,000 lbs. We were like kids with a new toy. The E models were re-engined with JT3Ds that put out 18,000 lbs of thrust so they didn't need water injection. I only really know about the tanker versions of the plane.
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Old 20th Nov 2022, 03:25
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Rick, I read that each wing had one water pump to feed both engines on that wing, so pump failure meant loss of thrust on both that wings engines. Systems can make life interesting.
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Old 23rd Nov 2022, 20:18
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I wish I could remember which aircraft my late father worked on at Wisley, Surrey, during the 1960’s. He was Technical Director for Elga Products Ltd as a pioneer and took Demineralisation cartridges along with him to trial high quality water in their aircraft engines. They proved highly successful.
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Old 29th Nov 2022, 22:33
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Since several posters brought up water injected JT9’s on some 747’s I have a few comments.

· Contrary to some above posts the water was injected into the combustion liner via the fuel nozzles.

· There were two water tank configurations. 747-100’s utilised the dry bay in the centre wing box between the front spar and 1st spanwise rib. The dry bay did not exist on 747-200’s so there were 2 tanks, 1 in each inboard wing leading edge.

· Injecting water into the combustion liner caused a thermal shock and metal fatigue and eventually there were instances of the combustion outer case rupturing on take off which blew the cowlings off along with other damage.

· Filling the demin water tank took quite some time as you had the honey truck servicing the mid lav’s, the potable water truck and the demin water truck all trying to get in the same area along with a catering truck at door 2R. On a quick turnaround it was not uncommon to be still pumping demin water in almost up to pushback, the demin water truck usually being the last to get access.

· The 2 operators of water injected 747’s I was familiar with appeared to use the water to lower the EGT in an attempt to prolong the hot section life of the -3A engine. They did not use it for the extra thrust and given the sector lengths they were flying from my location could even have used a derated thrust most of the time. I seem to recall they used water whenever the OAT was above something like 24C. One of the operators only filled the water tank to about 2/3rds of full.

· I have a distant memories of a trans Pacific operator of very early 747-100’s who started to retrofit the water injection system instead of upgrading their -3A engines to -7CN’s (which nearly everyone else did) but quickly changed course and abandoned the water retrofit and upgraded the engines instead. I have memories of seeing at least 1 or 2 of their older aircraft with all the water control panels fitted but inactive (it was over 45 years ago so memory might be playing tricks!!)
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Old 10th Dec 2022, 13:19
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Paninternational BAC 1-11 500 D-ALAR Flight 112

Sad case of Paninternational BAC 1-11 500 D-ALAR Flight 112 that force landed after take off and crashed on the Bundesautobahn 7 highway near Hamburg Airport Germany, killing 22 of the 121 on board on September 6, 1971.The BAC 1-11 had both engines fail on take-off.
The flight was enroute from Hannover via Hamburg to Malaga Spain.
The Investigation revealed the engine's Water Injection system tanks were inadvertently filled with Jet fuel Kerosene causing an overheat and seizure of both engines.
This was due to a handling and filling error the night before at Dusseldorf of the five water canisters.

While on the ground during the stop at Hamburg, the five water canisters were offloaded from the cargo hold.
The canisters should have contained demineralized water and were used to fill the engine's water tank giving better engine performance during the takeoff.
Manfred Rhode, co-pilot of the "D-ALAR" (975 flight hours), unsuspectingly pumped the contents of all five canisters into the water system of the BAC 1-11.

The airplane was prepared for the next flight to Málaga, taxi clearance was given to runway 34. Take off was commenced at 18:18.
The Captain had opted for a takeoff with water injection in view of the high ambient air temperature and their actual take-off weight for the full flight with enough fuel needed for Malaga.
Reaching a speed of V1 during takeoff, the crew noted a sharp rise in EGT.
Takeoff was continued and 2 loud bangs were heard.
The left-hand engine had failed, immediately followed by the right-hand Rolls Royce Spey engine.
The airplane was barely climbing through an altitude of 250m and the pilot pushed the nose down to gain speed.
The engines were not producing power forcing the crew to carry out an immediate emergency forced landing on the Hamburg-Kiel Autobahn E45 just 96 seconds after take off.
Due to the high sink rate the BAC 1-11 500 Jet touched down hard at over 200kmph.
The left hand main gear collapsed. The crew applied brakes to try to keep the airplane on the road.
The left wing and tailplane then struck concrete pillars of an overpass, causing the flight deck to break off and separate. The fuselage skidded and broke up, bursting into flames.
Men from the Hasloh volunteer Fire Brigade are the first to help at the scene of the accident, alarmed by the loud bang on the Autobahn.
When they arrive, it looks like a battlefield. "Shoes and bags, burst suitcases and mountains of luggage lay between countless pieces of wreckage strewn along the roadway."
The female first officer of the flight, Elisabeth Friske survived the accident. She sadly later died in a Cessna Citation accident on May 31, 1987.
99 of those on board miraculously survive the accident and the pilot and his two co-pilots survive in the torn-off cockpit.
Co-pilot Elisabeth Friske has a broken leg and is in shock. As firefighters try to free her from the cockpit, she says there's no way she'll leave the plane without the pretty sandals she had just brought back from Egypt. A fireman remonstrates with her, after which she lets herself be freed from the wreckage.

Investigation revealed that two of the five water canisters actually contained kerosene.
The canisters had been mishandled at Düsseldorf the night before and were then loaded on board the plane.
At the Investigation F/O Rhode denied not to have heard a warning from the loader Karsten Henneicke ("It stinks of fuel here") But Henneicke claims that Rhode replied: "Everything stinks of fuel here.''

Crew Photo: "Before the unfortunate flight on that day''.
Captain Reinhold Hüls (left) and the co-pilots Elisabeth Friske and Manfred Rhode with D-ALAR.

Last edited by rog747; 10th Dec 2022 at 15:10.
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Old 10th Dec 2022, 14:41
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Olympic Airways Flight OA411 Boeing 747 5X-OAA Athens 1974

The day when a Boeing 747 almost crashed on downtown Athens, SX-OAA, named Olympic Zeus,
The Captain Who Broke The Rules and saved 418 Lives (398 pax and 20 crew)

Olympic Airways 747 almost crash Athens 1974

Flying from ATH to JFK in August 1974 during the take off run on a typically hot Athens summers day the 747 was using water to assist the engines with extra thrust when a loud bang was heard but the Captain elected to continue the take off.
The aircraft just cleared the boundary fence and then against the Company rules Captain Migadis elected to raise the gear.
He then traded some 50' of height for more speed.
He thought well, we were all dead, it's over. The aircraft was carrying 160 tons of fuel, as it would fly directly from Athens to New York.
In the main cabin Cabin Crew member Lucia Siachou got an intercom call from a colleague seated right at the back who had seen engine number three on the right hand side had blown up. The colleague said “we are screwed” and she just replied with “I Know”.
Controllers in the tower watched on in horror as they watched the plane struggle to gain altitude heading towards the City.
The Captain's reasoning for raising the gear was that he needed speed in the long term, he had a hill in his flight path and there was no way that he'd be able to clear the hill with the gear down slowing the plane down.
He was relying on his decades of experience and so he made the call.
The controllers watched as the plane barely gained any more altitude once the gear was up but soon the plane gained a bit of height, probably whilst still in Ground Effect.
But the 200 foot tall Panos hill was now barely a mile away. The captain did not have a choice; he pulled the nose up as the airspeed he had built up so far bled away.
The 747 Jumbo Jet cleared the hill by 9 feet.
But this was far from over, climbing to avoid the hill had cost him precious airspeed. He now had to drop the nose again to speed up otherwise the jumbo jet would drop out of the sky.
The captain decided to trade more altitude for about 6 knots in airspeed. It wasn't much but it would keep them from stalling.
At this point the jet was still so low that it barely cleared cleared some Radio and TV antennas.
But little by little Captain Migadis in his 747 managed to gain more height and speed and so then slowly turned and headed out over the sea where the air temperature dropped a little thus gaining even more height.

The crew barely able to keep the plane airborne, had been flying just 200 feet above a densely populated area of Athens. Airspeed was exceptionally slow, the FDR showing as low as 158 kts, which was not possible according to Boeing.
Later attempts in the Simulators would result in crashes at every attempt to recreate the same flight pattern.

After almost two minutes flying straight and as low barely 50m above the ground the captain was able to gain some airspeed and finally altitude up to 1,500ft over the sea.
After quickly dumping fuel over the water, the plane landed safely back at Ellinkon, some 30 minutes after takeoff.

It was discovered that the #3 engine's water injection system was mistakenly turned off prior/during takeoff, causing the engine to overheat and explode during rotation.
The water injection for engine #3 was switched to 'On' during the ground checks, but the F/E inadvertently switched it 'Off' before or during the take off.

There was a very complicated water injection system that could be used with the following early JT9D engines on the 747 :
JT9D-3A, Dry T/O rating 43.500 lbs. Wet rating 45.000 lbs.
JT9D-7 and -7H, Dry T/O rating 45.500 lbs. Wet rating 47.000 lbs.
JT9D-7A and 7AH, Dry T/O rating 46.150 lbs. Wet rating 47.670 lbs.
JT9D-7F, Dry T/O rating 46.750 lbs. Wet rating 48.650 lbs.

Water alone is specified and should contain no more than 10 (ppm) parts per million impurities.
Use of water is limited to takeoff operation up to an altitude of 8,000 feet at the minimum ambient temperatures of 32F.
Take off using water injection at max takeoff power is limited to a maximum period of 5 minutes including operation with water injection for not more than 2 1/2 minutes

On the 747-100/200 two water tanks were each built in the wing roots (left and right) and extra piping was installed for transportation of the water to the four engines (one tank for 2 engines at the same wing.) Also piping for water filling and draining of residual water after T/O was installed.
Four high capacity water pumps were feeding the engines with water.
Each engine had an adapted fuel control to cater for extra fuel when the system was activated.

System operation (747)
- When a wet rating was needed min. 2300 kgs of water was uplifted. (standpipe level was 2450 kgs)
- During Taxi-out, just before entering the runway, the system was switched on (F/E panel), the four water pumps were momentarily giving a flow indication (four green lights), check all water low press lights out. Most frequent failure at this moment : water pumps start to operate but the water shut off vlv is still (partly) open. This is called a "steam out".
The relevant engine (still at idle) gets the full water flow and stops operating and has to be restarted, after switching off the water injection system.

When entering the runway the system is now armed.
After advancing the powerlevers at approx. 1.25 EPR the system comes in, four green water flow lights illum (pilots annunciator panel), the water shutoff valves are open.
Careful monitoring of the EGT indication is crucial (one engine can suddenly revert to no water (pump failure), but still with the high (wet) fuelsetting.
After 2.30 minutes or just before water run out (indicators on F/E panel), the system is switched off.
Switching off was the most tricky part of the operation, because of the low usage of the system frequently failures occurred.
The most dangerous was that the water pumps stopped and shut off valves closed but one engine fuel control stayed at the wet fuel rating.
Before you could blink an eye the EGT exceeded the T/O limits and an expensive horoscope check or even an engine change was required.

From a KLM friends 747 crew perspective - Wet Take Offs between 1978 and 1990 on KLM 747-206B aircraft.
Most of them on the AMS-LAX NBO-AMS and AMS-IAH stretches, nearly always air-conditioning packs switched off enables more thrust from the engines.
All three of us in the cockpit were always fully aware that in fact this aircraft was underpowered when at MTOW, and the engines required a lot of extra attention during these kind of Take Offs plus at Hot and High airfields.
The engine sound of the 4 P&W JT9D-7W changed to a very low growling sound when the water injection came in at approx. 1.25 EPR powersetting. Most of the time we left the brakes on a little longer as so to gain some runway length and checked that all four green waterflow lights were illuminated.
After the"Water on" call the brakes were released.
With four growling engines it took a very long time before Vr was reached. It always looked very close to the end of the runway.
Slowly climbing with mostly MTOW (351.000 lbs) we climbed away until the water was almost running out or 2.30 minutes was reached.
Now "water off" was called by the F/E to warn us pilots for the impending thrust decrease.
Power levers were retarded a little bit, before actual stopping of the water injection system on the F/E Panel.
This was done to prevent an overboost during transition to the Dry setting.
Now GA or CLB was selected at the engine mode select panel and depending climb out procedures, GA or CLB thrust was set.
Especially after selecting the 'water injection off' and setting CLB thrust it became very quiet in the aircraft, so sometimes the captain warned the passengers before take off, that after take off the engines were only retarded and had not stopped!
KLM 747's at first had the -3AW engines but these were changed to -7W or -7AW.

I gather that also the Northwest Airlines DC-10 series 20 (as it was actually known, but monkiered as the -40 series) were fitted with PW JT9D-20/20J engines that would come with water injection and all of these DC-10 -20's were equipped with water injection and were certified with the water injection system working. The aircraft were "never" operated AFAIK in service using the water injection.
Both the JT9-20, and -20J had been equipped with water injection but this was removed later on to save weight.
At first some of the aircraft water injection lines were removed to ease maintenance in the LH wheel well, the wing leading edges, and the engine pylons in the early 1980s.
The rest of the system was removed, other than the tank, in the early 1990s.
The water tank is mounted on the lower LH side of the fuselage, just aft of the wing, and looks like a body fairing. The drain mast for the tank is just below the aft or bulk cargo door, just left of the centerline of the belly. The tank held 600 gallons of demineralized water. There were three pumps located in the tank.
The only parts of the water injection system that were left on the engines were the fuel nozzles with the water injection ports capped off.
There was never a ' W' in the engine's designation on the data plates for either engine.
The JT9-20 was a JT9-7A that was adapted for the Douglas application, which means that the gearbox was mounted under the fan case.
The JT9-20 had a takeoff EPR of 1.46, and put out somewhere in the neighborhood of 44,000 lbs dry thrust, without water.
The JT9-20J was a JT9-7F, that had the turbine section out of the -7J, and a different fuel pump than a -20.
This engine had a takeoff EPR of 1.51, and put out roughly 48,000 lbs of thrust dry, or without water.
The -20J had a higher max EGT limit than the -20.
These two engines side by side were basically identical.
All of NWA DC-10-40s were certified at 535,000 lbs gross weight, so a -20J powered aircraft simply had more power and these aircraft were used on different routes.
In the mid 1980s P&W offered to convert the NWA DC-10-40s to JT9-7R4 power, like they did at JAL, but the aircraft was being looked at for retirement at that time, so they passed on the offer, but the NWA -40s actually stayed on for another 18 years or so.

The NWA DC-10-40s were actually DC-10-20s...Donald Nyrop, who was the CEO at the time had ordered his DC10s with the JT9s and the extended range upper and lower auxiliary fuel tanks, longer wingspan, center gear, and so on.
He then found out that Douglas was going to hang CF6-50 engines off of the same airframe, and call it a DC-10-30, well he flipped out and basically demanded that his P&W powered DC-10s be re-designated as -40s...He wanted to have the higher number, not to be outdone by the new and higher numbered -30s that would follow and show the World he had the 'better' DC-10.

While working on the DC-10-40, one would find numerous bookwork and data plates on parts of the aircraft that pertained to the P&W application, and they would be stamped DC-10-20.
The upper and lower auxiliary fuel tank access panels were also stamped "DC-10-20/-30 only".

Last edited by rog747; 10th Dec 2022 at 15:13.
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Old 10th Dec 2022, 16:46
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Very informative post, rog747! Thank you for taking the time.

- Ed
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Old 11th Dec 2022, 11:02
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Thanks for the info rog747.
I operated B747-238 with P&W JT9-7AW engines. These aircraft used 2400Kg water, 600Kg per engine for 2.5 minutes on takeoff. We FEOs checked the gauges carefully coz we needed the lot.
There was only ONE water pump switch on the FE panel fwd knee panel for all pumps along with the lights as described. Of that I am absolutely certain, definitely no individual pump switches.
As I recall it the water tanks were plumbed such that one tank fed inboards and the other fed outboards. It was also necessary to ensure that Galley Power was switched off after start prior to using water coz the AC system could not support the load if the GP did not automatically switch off when Water On selected.
Calculating performance data for a wet takeoff was an absolute nightmare. Three of us would fish the numbers out of our performance manual independently and regularly came up with three different answers usually 3-4 tons MTOW difference. It mattered when we were operating PER-BOM return and BKK-ATH return coz every Kg of fuel was needed and we had lots of cargo offered.
Ah the Good Old Days!!
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