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Old 25th Dec 2012, 20:42   #21 (permalink)
 
Join Date: Jan 1999
Location: north of barlu
Posts: 5,260
Dutch

I have to disagree with you, the reason the nose leg may be slow to disengage from the centering mechanism is that the oil/air quantitys are wrong in the landing gear shock struts, what you are describing is a defect with your aircraft and should be addressed by your maintenance provider, not by putting extra stress on the nose gear when landing.

As for fuel tank usage the main tank has a problem in that the last 10 lts or so can't be used in the climbing attitude and so the main tank should NOT be used for landing in a low fuel situation. From an endurance point of view it is far better to run the main tank dry in the cruise and land on one of the wing tanks. That way you can burn all the fuel on the aircraft rather than have the engine stop in the go-around dispite having enough fuel in the tank for another circuit.

I suspect that the later DR400 & 500 that were manufactured may have addressed the unusable fuel in the climb due to the different shape of the main tank fuel pick up, but if you use my SOP it is good for all DR400 aircraft.

Of course I would recomend not getting the fuel that low in the first place but you should know what to do if fate gangs up on you !

Last edited by A and C; 25th Dec 2012 at 20:52.
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Old 25th Dec 2012, 20:52   #22 (permalink)
 
Join Date: Aug 2001
Location: UK
Posts: 2,352
IIRC but no POH here to hand is that you HAVE to use the mains for take-off and landing, not the wing tanks; that makes a bit of sense too as there are variants for the DR400 which only have the mains tank - no wing tanks nor the auxilary fuselage tank.

Re Nose Gear; the steering engaging/disengaging mechanism is a purely mechanical affair; nothing to do with the strut air/oil bits, although a low strut due to lack of air/oil will make the symptoms described worse; not better.

But happy to stand corrected as I know nothing.


Last edited by Flyin'Dutch'; 25th Dec 2012 at 20:54.
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Old 25th Dec 2012, 21:12   #23 (permalink)
 
Join Date: Feb 2007
Location: Amsterdam
Posts: 4,387
No POH to hand either so I cannot confirm or deny, but having to use the main tank for take-off and landing is something I have not heard before. It's also not in the club checklist. And I can confirm that the aircraft takes off and lands perfectly fine on the saddle tanks - but I have to admit I have never come close to running one of the tanks dry and I would not want to land or take-off with an almost-dry tank selected in the first place.

What I have done, and which may serve as a warning to others, is select the fuel selector "off" while I intended to select the main tank. We were at 1000' when it happened, and fortunately my pilot passenger caught my mistake immediately. Otherwise we might not have recovered in time. Reason is the on-ergonomic design of the fuel selector, where backwards is the main tank, and forward is shut-off.
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Old 25th Dec 2012, 21:15   #24 (permalink)
 
Join Date: Jan 1999
Location: north of barlu
Posts: 5,260
There are a number of issues of the flight manual but for the two aircraft that I have owned there was a warning that fuel flow from the main tank was not assured in the climb attitude when the low quantity warning was illuminated, the first aircraft I had was a DR400-140 with only the main tank fitted, my current aircraft (DR400-180) has the same warning in the flight manual but no limitation in which tank to use for take off and landing, I would send you a copy but the FM is in the aircraft, not at my desk.

You are correct about the nose wheel centering mechanism being mechanical but it operates as a function of nose leg extension and is engaged at the last 20mm or so of leg extension.

So if the nose gear is extended to far, ether by being over extended by over pressure in the nose leg or under pressure in the main gear legs then this will effect the disengagement of the centering lock.

Unfortunatly this is not a simple matter of air pressure in the legs as the oil level in the legs is critical to getting the correct rising spring rate from the leg and therefore the correct ground attitude for the aircraft to ensure that the centering lock disengages when it should.

To get the legs set up correctly you will have to jack the aircraft free of the ground and check and adjust the oil level in the legs before pressurizing the leg to the correct pressure for the variant.

It is essential to understand that just pumping up the air in the leg to get the correct extension is useless without the oil level being correct as this will not provide the correct rising spring rate.

Last edited by A and C; 26th Dec 2012 at 08:34.
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