Recent Topics - Rotate.Aero Mon, 26 Jun 2017 03:27:24 +0000 MYOB en-gb ACARS Event Times - by: Mark
ATA 23 Communication Fri, 23 Jun 2017 00:57:43 +0000
ATA 22-10, Auto-Land Failure - by: Mark

The Auto-Pilot uses wheel speed signals to initiate the nose-down and roll-out landing functions. The FCC's look for 80 knot wheel speed signals during take-off. The thinking is...... if one (or more) transducers is failed at the beginning of flight, than the failure will be present on landing which would prevent proper auto-land operations.

The Auto Ground Spoiler system looks at these same transducer signals for wheel spin up also.

On MD-10's and MD-11's, every tire has a transducer used for Anti-Skid, but only the rear set of tires is monitored for speed by the FCC's. The failure above showing the LIB (Left InBoard) would be the #6 main tire.

The transducers can be monitored through CFDS, FCC1 (or FCC2), Sensor Readout, Analog Inputs.

The left inboard does show "something" in the image above, but all the tires are at rest. The failure would most likely be either a sheared transducer shaft or a open signal coil. There would be no speed increase as with the other three tires. The FCC's would log this fault almost instantly. All the flights referenced for this failure had the fault recorded before 500' of altitude.

MD-10-10 ASM 32-45 and 27-63.]]>
ATA 22 Auto-Flight Wed, 21 Jun 2017 02:08:18 +0000
ATA 28-42, Fuel Stick - by: Mark

The stick sits inside a sealed tube. The magnet on the tip of the stick is acted upon by a float that rides up/down around the tube.

Replacement of the stick takes less than five minutes.

A simple snap ring holds the assembly in place. A pocket screwdriver was all that was needed to snap this ring in.

MD-10-10 AMM 28-42-01-2]]>
ATA 28 Fuel Mon, 19 Jun 2017 23:18:17 +0000
ATA 29-12, MD-10-10 Hydraulic Pressure Low - by: Mark non-avoidable discrepancy dealing with the #1 hydraulic pressure. With spoiler handle movement, the pressure on the #1 system was consistently 500-700psi lower than the #2 and #3. This was accompanied by the indication going amber. (The pressures are pretty close in the image below. This is a recovery phase with no spoiler movement and pressures climbing.)

So what could I be dealing with, a bad indication or a bad reversible motor pump? What did I "hope" it was?

There is one quick way to verify the fault in this case. Turn off the electric pumps and crank an engine to be used as a pressure source. The engine does not need fuel applied. The starter alone will fully pressurize the engine driven pump(s).

In the case of this aircraft, with the #1 engine spinning I had 2900psi and it only dropped a hundred pounds while moving the flight controls.

Verdict??? A weak reversible pump and a nasty ass replacement procedure.

There is no way two electrical pumps will ever generate the power of an engine driven pump. With the electric pumps, all the pressures will be low, but not to the level that was noticed with the #1 system. It is also a testament to the strength of the starters.]]>
ATA 29 Hydraulic Systems Mon, 19 Jun 2017 02:53:29 +0000
ATA 76-12, GE CF6-80C2A5F Engine Fuel Solenoid - by: Mark
One thing to keep in mind is that the solenoid acts similar to a latching relay. It will maintain its current condition until a command (in this case 28VDC) to change state is applied to one of its coils. In other words, if its closed it will remain closed until 28VDC is sent to the open coil and it will remain open until that voltage is applied to the closed coil.

I'm going to have to guess that the engineers did not want power applied to the fuel solenoid on a full time basis. Either there was a heat issue or longevity is increased without voltage always present.

Relay 37KC is basically "on" 99.9% of its life and for anyone who has brushed up against a A300 relay rack...... it's one of the ones that burns you.





Fuel Solenoid and Pressure Switch

Fuel solenoid end view and side view showing an extremely fine mesh.

A300-600 ATA 76-12 Engine Start Solenoid
ASM 76-12-00
ATA 76 Engine Control Sun, 02 Aug 2015 00:11:35 +0000