Topics in Category: MD-10 - Rotate.Aero Wed, 24 Jan 2018 09:55:52 +0000 MYOB /media/kunena/images/icons/rss.png Topics in Category: MD-10 - Rotate.Aero en-gb ATA 28-42, Fuel Stick - by: Mark ATA 28 Fuel Mon, 30 Oct 2017 23:37:39 +0000 ATA 29-11, MD-10-10 Engine Hydraulic Pump Verification - by: Mark ATA 29 Hydraulic Systems Thu, 19 Oct 2017 22:59:57 +0000 A/C Bus Tie Disconnect - by: Mark
ATA 24 Electrical Power Wed, 23 Aug 2017 01:19:15 +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 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 33-51, Emergency Lights - by: Mark ATA 33 Lights Fri, 26 May 2017 02:52:55 +0000 ATA 23-24, ACARS - by: Mark
This video shows a quick and dirty reset procedure for erasing previous flight reports stored in the ACARS system. This procedure can be used in case of an outbound crew initialization lock out.

ATA 23 Communications Fri, 26 May 2017 01:25:30 +0000
ATA 24-21, CSD Underspeed Switch - by: Mark
Per the MEL procedures, the #3 CSD was disconnected and the aircraft dispatched.

When I approached the aircraft, I found these indications for both the electrical page status and the overhead.

The troubleshooting was not mine, but the thinking was that the CSD underspeed switch was at fault. The reason behind this was if the underspeed switch was showing the CSD running, but there was no output power...... the GCU would interpret this as a fault and generate the fault lights observed by the mechanic.

Given the choice of changing the CSD or......

changing the switch, it was quite obvious which we going to try first.

The switch is located on the forward side of the CSD. The replacement was quite simple and quick.

After re-engaging the CSD and starting the engine, the generator showed online with no faults indicated. (This picture shows the generator output of 115VAC and 400Hz. The #3 generator contactor is closed and the #3 bus-tie contactor is open.)

I'm somewhat perplexed as to the switch's operation. In the schematic manual, 24-21-1 and 24-11-2, it shows the switch coming off an output leg of the generator's PMG (Permanent Magnet Generator) with the resultant signal feeding the GCU. It appears the switch is activated by oil pressure which pushes down on a plunger. The plunger acts upon a coil inside the switch. The only thing I can guess is that the coil's inductance is changed with the position of the plunger???? No explanation is given in the Maintenance Manual.

MD-10-10, CSD Underspeed Switch R&R, AMM 24-11-06-2]]>
ATA 24 Electrical Power Wed, 24 May 2017 17:17:24 +0000
ATA 33-44, Nav Tail Lights - by: Mark

These bulbs are 10VAC bulbs. There are transformers in the wing tips that convert 115VAC down to to 10VAC. These transformers receive their power from two separate relays. Two lights forward, two lights aft, and two transformers on each wing tip. Two lights (one forward - one aft) are powered by one relay/transformer set. If one relay/transformer set fails, there will still be two bulbs illuminated.

I have changed plenty of relays, but not one transformer. The relays actually power a transformer in each wing. It's almost a given when doing a walk-around and seeing four bulbs out (one at each pair) that you've lost a relay or a breaker is popped. Airbus aircraft (at least the A300) use the same operational voltage.

Inboard socket pulled out. The strobe light has to be pulled out to remove a socket screw. Wires pretty dang short, but enough room to get to the screws.

MD-10 Navigation Light Socket R/R, AMM 33-44-00-4]]>
ATA 33 Lights Wed, 17 May 2017 01:49:55 +0000
ATA 34-42, Radio Altimeter - by: Mike Forti ATA 34 Navigation Wed, 10 May 2017 13:20:44 +0000 ATA 22-12, MD-10-10 Roll Actuator - by: Mike Forti ATA 22 Auto-Flight Sun, 30 Apr 2017 10:30:36 +0000 ATA 23-51, Yoke Mic Switches - by: Mark
Before even powering up and going upstairs, you head to the E&E to reconnect the wires that were removed for the MEL.

This is actually the cover for the Capt's yoke disconnect. The F/O's looks just the same on the right side.

The wires in question have yellow identifier sleeves and the elongated holes of terminal 41 pretty much shout out to have the pins stuck back in. The wires are still wrapped in orange tape.

The red end of the red/white plastic tool is used to lock them into place.

Now...... let's go upstairs.


No heat shrink and the switch base looks a tad bit burnt.

The switch actually has a forward (Interphone) position and a aft (Radio R/T) position. Let's figure out the orientation before shoving it home. A quick call to the shop on VHF verifies pin 5 should face aft with the switch inserted. Let's try the interphone...... it doesn't frickin work.

A return trip to the shop for a meter and a quick glance at the prints...... this shouldn't be to hard, should it? Two wires (2 & 6) should have continuity and two wires (1 & 5) should read "something" back into the Audio Management Unit (AMU). Let's hit it.

2 & 6 read good. Pin 5 reads approximately 1 Meg-Ohm. 1 reads open, but 4 reads approximately 1 Meg-Ohm also. So...... 4 and 1 are swapped. A little solder work (with heat shrink) and now the interphone works, but hey...... the switch base has swelled out and it WILL NOT fit in the hole. Gosh, I wonder why someone was in such a rush to leave.

A new switch soldered correctly with heat shrink over every solder joint and the job was done...... well 2 hours worth instead of around a half. Oh-well, sometimes you have to deal with this crap.

By removing the two wires for the MEL, you're basically taking the "return" signal for the switch to the AMU out of the picture. With both of them out, neither the interphone nor microphone will be activated from the yoke. There's a switch on the window console for the radios and a switch on the audio panel itself for either function.

MD-10-10 WDM 23-51-01
IPC 23-51-15-03
AMM for switch replacement 23-51-08-2
ATA 23 Communications Sun, 09 Apr 2017 04:12:08 +0000
ATA 32-45, Anti-Skid System - by: Mark

Previous troubleshooting was limited and as par for FedEx...... a wheel speed transducer was changed which did not cure the problem.

A quick glance at current anti-skid faults, showed......

The Anti-Skid Control Unit is in the center electronics bay. A comparison of transducer and manifold valve resistances was needed to "at least" rule out a wiring fault.

A reading on the #2 transducer (pins 12 & 13 of plug "A") showed a resistance of 295 ohms. This matched several other transducers.

Just to note a typical manifold valve, several coils were also checked. All valve coils are on the bottom (or "B") plug.

All the valve coils checked, fell in around 215 ohms.

At this point...... I would think an Anti-Skid Controller would need to be tried next.

MD-10-10 ASM 32-45-0]]>
ATA 32 Landing Gear Wed, 22 Mar 2017 01:26:18 +0000
ATA 28-23, APU Start Pump - by: Mark

AMM 28-23-00-0
FIM 28-23-00-2
ASM 28-23-2
ATA 28 Fuel Fri, 13 Jan 2017 05:07:33 +0000
ATA 21-30, MD-10 Cabin In-Flow Low - by: Mark ONE thing. It's got-a hole in it.

We took this thing to 4psi differential and "walked" the aircraft with three people. Some cargo door seals were puking a "little", but when a hand was drawn across the A/C hook up doors....... the problem was pretty much obvious before the aircraft was equalized and the access door opened. (and NO.... the mechanic did NOT want to even open a simple non-sealed door, because there really was a huge amount of air coming out the edges)
I'm glad the problem was found. I'm not glad it took 2+ months of flying around the system with 10+ write-ups....... pretty piss-poor.



MD10-10 ATA 21-31-00 Pressurization
Fault Isolation Manual 21-31-00 Task 803
ATA 21 Air Conditioning Tue, 04 Nov 2014 23:22:13 +0000
ATA 21-50, MD-10 Pack Outlet Temp Sensor - by: Mark
Compared pins "e" and "f" (both little) at pack temp controllers. These connect to the outlet temp sensor. Found #3 open while #1 & #2 read approx 1.7k ohms. Shot the sensor directly to eliminate wiring.... it was open.

MD-10-10 ATA 23-50 Pack Temp
Schematic 21-50-1
ATA 21 Air Conditioning Mon, 20 Oct 2014 23:01:59 +0000
ATA 22-30, MD10-10 Auto-Throttles - by: Mark

MD-10-10 ATA 22-30 Auto-Throttle Troubleshooting
Maintenance Manual 22-31-03-4
ATA 22 Auto-Flight Mon, 14 Jul 2014 00:49:00 +0000
ATA 29-12, MD-10-10 Hydraulic Pressure Indication - by: Mark Not much troubleshooting needed here. Hang a new sensor on the plug. If problem clears, get ready for a possible Skydrol bath (even with head pressure blown, I still received a "goodly" amount of fluid).

MD-10-10 ATA 29-12 Hydraulic Pressure Indication
Schematic Manual 29-10-1
Maintenance Manual 29-12-46-2
Equipment List ID "T2-39"
ATA 29 Hydraulic Systems Mon, 14 Jul 2014 00:42:51 +0000
ATA 30-42, MD-10 Window Defog Troubleshooting - by: Rotate Admin

Video covering troubleshooting of a window defog problem. Tools used were a VOM, Amp Clamp, and one brain. The weakest link was the brain. Window "DEICE" controllers were swapped early on instead of the defog controllers which added considerable time and questioning of thought processes. Isolation of sensors was not explained very well either. But...... window heat current and voltage in action might help others to understand the system.

MD-10 ATA 30-42 Window Defog Systems
AMM Reference 30-42-01-4
Schematic 30-42-01
ATA 30 Ice/Rain Protection Sun, 13 Jul 2014 23:28:18 +0000