The fun of muti engine operations
Yesterday we went to Tibenham to a local closed meeting for a mixed Warbirds and jets event that are held regularly there. It is fortunately close to my home.
I took the Arado to try out the new retracts I had fitted in an attempt to get the legs to retract. For those that have not followed this plane it has 6 engines, all home built Sprite engines of same size as the P20 and putting out 3.2 Kg each. For simplicity I went for a hand start operation with this plane. This reduces the requirement for a ridiculous number of wires to connect each time we fly. As it is there are 6 computer plugs to connect the engine pod to the plane and 6 pipes. It is a large plane with 3.35M wingspan and weighs 31 Kg. The centre section only just fits in my car and my long suffering wife has to be co-opted to get the centre section in.
After a number of outings we have learned to number everything. Again for simplicity I have 6 ecu’s 6 tanks 6 pumps etc. Believe me this does make for complications and is much more than 6 times the aggravation getting them all running. Everything was checked out and I had all engine ecus reading revs and temperature correctly.
This time I fairly quickly got the plane assembled at the field and to fuel it up and demonstrated the retracts working. We then went to start the engines about mid day.
Start no 1 went ok till I reached engine number 3 and the ecu display refused to show its information, which is vital when starting manually. After a rethink I managed to bypass the single display for this engine and added a second display for engine 3.
Start no 2 was a real problem as engine no 1 ecu temp probe had failed (my first one ever) a quick drive home and I brought a spare to the field and bypassed the wiring loom withe the new thermocouple.
Start no 3 we started engine 1-3 quickly but engine no 4 refused to come up to idle. There was fuel flowing to it but not enough. We stopped engines and I checked ecu settings and they seemed ok and I could get fuel flow manually from the ecu. Eventually we wondered if a pipe had got kinked. A quick examination of the engine pod revealed the fuel line was pinched when we assembled the engine pod.
Start no 4 was successful and all engines were running so we were in a position to go flying!
Until now we had all 6 engines running the whole flight but flight no 1 of the day was to prove different! The takeoff run had just reached lift off point and one engine flamed out and then a second as the plane staggered into the air. We really had reached the point of no return and I could see we were nearly airborne. A few circuits later Dave landed safely much to our relief. We were pleased to have discovered that the plane would fly on 4 out of the 6 engines.
Although there didn't appear to to be much wrong with the 2 engines I replaced them anyway with spares.
The next start had to be aborted when we had 4 engines running as the starter fan batteries had died on me with all the aborted starts.
Finally we had all engines running again and went for the second flight. This was a bit of a repeat as the first flight and 2 engines died on us. Despite this Dave managed to gain some height and relax a bit and we were able to try the retracts which needless to say didn’t work as I did not have quite enough air pressure. We flew about for 4 minuits or so and then landed with a second nice landing. We were amazed when we landed to find that we had flown most of the flight on only 3 engines although the poor little things had been flat out most of the time. Astonishing that a big heavy plane of 31 Kg can be flown on just 9.6 Kg thrust.
After landing only 1 engine had mechanical issues so I am not sure why the others failed. All this took most of a very stressful day and I hope that I was not too short with anyone. When I get back after flying complicated planes like this I vow not to fly them again and go back to simple one engine planes, but there is no doubt people love to see them.
John