Topics in Category: GII - Rotate.Aero Wed, 23 Jan 2019 01:39:14 +0000 MYOB /media/kunena/images/icons/rss.png Topics in Category: GII - Rotate.Aero en-gb ATA 80-11, Starting - by: Mark
We were wrong. After the starter was removed, giving a clean view of the switch cannon plug..... both wires were hanging by just a few strands (which would explain the intermittent problem). The wires were repaired and the original starter re-installed.

Some folks might question how 28VDC was read at the plug on the engine: A relay coil can be considered as a regular wire when the relay is not energized. The relay is not working (dropping the voltage) so a full 28VDC can be read on the back side of the coil. If the relay were energized, 0VDC would be read, as the wire is now grounded and all voltage is dropped through the relay coil. Short explanation. ]]>
ATA 80 Starting Wed, 09 May 2018 01:31:55 +0000
ATA 27-06, Flaps - by: Mark ATA 27 Flight Controls Mon, 30 Apr 2018 20:56:10 +0000 ATA 22-00, Trim Switch Replacement - by: Mark

The switch uses a solenoid to maintain it in the "on" position. I found if it was held up just a tad bit longer than normal (a couple seconds), it would remain engaged. You could smack it and have it drop off (not every time, but just once is an indication that the switch is weak).

As par for the course with these older aircraft...... no extra wire to do your work. A couple tie-wraps to hold it out helped.

I treat these just like a multi-pinned cannon plug, Start at one edge and work your way to the other side. I care about making sure I get the connections right, but I care not the number order I do them in.

The replacement fixed the problem and the "yoke actuators" could re-enter their nirvana "auto" mode again.]]>
ATA 22 Auto-Pilot Thu, 11 May 2017 17:46:16 +0000
ATA 29-30, Combined Hydraulic Pressure indication - by: Mark
I was presented with a Combined Pressure Indication problem. The gauge was reading 0 at all times.

One problem was quickly noted. This is a Combined System and Flight System pressure dual indicator. All the prints in Gulfstream's wiring manual show separate indicators for each system. It took some time to find the outfitter modification showing the correct pin-outs.

The pin-outs for the dual Utility and Aux pressure indicator are the same.

We're only talking four wires here. "A" is ground at both the indicator and transmitter. 26 VAC should be on pin "B" on both also. "C" and "D" are the signal wires.

The transmitter for the Combined System is in the hell-hole on the left hand side.

The plug on top had previous douses of hydraulic fluid, as the rubber insulator was basically mush. It was still doing it's job of separating the pins, but a plug change needs to be accomplished.

I checked all the associated wires from front to back for proper power, ground, and continuity. I also checked the wiring to each other as an aircraft this old could easily have broken insulation. The plug length behind the indicator was a joke, with not even enough to pull through the hole.

All the wiring was good. The first transmitter replacement was bad...... the indication returned with a second transmitter.
The transmitters are quite an interesting component. There is actually an internal electrical amp controlled by something called
a Bourdon Helix.
A good explanation of how it works can be found here.

GII, AMM 29-01-00
AWM 29-32-00
ATA 29 Hydraulic Systems Wed, 29 Mar 2017 00:08:23 +0000
ATA 22-00, Auto-Pilot Engagement - by: Mark ATA 22 Auto-Pilot Mon, 05 Dec 2016 03:45:22 +0000 ATA 24-01, Emergency Transformer Rectifer - by: Mark
Maintenance reported that when the aircraft was taken off external power (battery switch off also), some circuits stayed powered on what should of been a dead aircraft.

I isolated the batteries by disconnecting the plugs. The problem was not prevalent with just the #1 battery connected, but it damn sure was with the number #2..

After looking at the schematics, I started pulling breakers to narrow things down. I found that by yanking the #2 Emergency Battery circuit breaker, power dropped off.

Back to the prints....... the #2 Battery Emergency Contractor (relay if you want) was staying on. Power to X1 of the coil was supplied hot by the battery itself. So.... I've got a relay with coil power designed to be present at all times. I've got to find the ground that is causing it to remained closed. Back to the prints.... which with Gulfstream can be a real bitch to trace out across 17 pages.

Anyway.... it turned out to be that the Transformer Rectifier Switch was in the "ESS' or down position. This switch is normally off and really only used in the "MAIN" or up position when running the APU. If this switch is left in anything other than "OFF" when power is removed, it'll do what its supposed to do..... keep the basic stuff up and running.

The switch would absolutely be needed in flight if both engine driven generators took a crap. The aircraft could still be fed DC power using one of the two engine alternators as input power to the Emergency Transformer Rectifier. Its job is to convert the wild (floating frequency) AC into DC. Depending on the severity of the situation, both main and essential DC buses can be fed or the system can be isolated to just the essential.

(For those of you in the commercial world, the majority of corporate aircraft power is derived from DC engine driven generators)

AMM 24-01-09]]>
ATA 24 Electrical Power Sat, 23 Apr 2016 02:07:40 +0000
ATA 24-01, Battery Monitoring - by: Mark This aircraft had a hard fault for Battery #1. The amperage indication was pretty much stuck on "88" while the the #2 battery was reading correctly.

Overhead Indicator (Poor image.... digits cannot be seen.)

The Battery Warning Amp is located in the 169 panel.

There are two plugs..... unfortunately, they're on the outboard side, but still reachable.

The amp is actually "two" amps in one box. One for each system. The plugs are keyed the same and can be swapped. When they were, the #2 Battery was faulted. An amp was ordered.

This is a nice feature that I've seen on some of the older Gulfstreams for other systems

Also as a tip, DC Amperage measurement uses shunts as the sensing source. A quick look at shunts on an Airbus

Two items of note:
1. I haven't seen a GIII as of late, but I'm pretty sure they use the same type system.
2. Some GII's (and maybe GIII's) have shunt bypass relays that are used for APU start. I'm assuming that the starter draw on the batteries was burning out the shunts, so while the starter is engaged the majority of current is using the relays as a path instead of the shunts.

AMM 24-01-11 AWM 24-30-00]]>
ATA 24 Electrical Power Sat, 23 Apr 2016 00:35:34 +0000
ATA 23-70, GII CVR - by: Mark
Simple call-out for reset of "G Switch". The red light bulb was burnt out so it gave no indication of a switch problem.
A quick press did not reset it. It took about a five second hold-down.

There are still a ton of aircraft with this type of installation out there. The possibility of a "G Switch" being installed should always be considered before troubleshooting.

No print in Gulfstream WDM. A schematic is in AMM.
ATA 23 Communications Mon, 20 Oct 2014 23:20:05 +0000
GII Compass - by: Mark

Without digging into prints. I'm taking this all from my failing memory banks, so if anyone can correct me.......please do.
In the system shown in the video, I'm pretty sure the amp is the main "computing" component. Without gutting it, I'm sure there is a row of synco's that outputs information to all the user systems - RMI and HSI for the compass indication, but also outputs for the nav receivers, auto-pilot, comparitor, and maybe even the FMS's.
The sync indicator "is" on the RMI, but the amp is commanding the gyro torque motors.

With an old RMI (C4 or C14 type???) like this one.

The RMI is the workhorse. The Compass Rack would have two removalable amps, servo and slave. There would also be a circuit breaker on the front face of the rack. This breaker is the 26VAC for the flux valve. The HUGE issue with these older systems is the plug connection at the RMI. A plug that isn't seated "fully" will cause all kinds of crap to occur with the compass system or outputs. ( I did a road trip to Austin on an MD-80 to fix a bad #1 compass. My fix???? Pull the capt's RMI, verify no bent pins, and re-install plug TIGHTLY. Problem solved and I still had some time to go slug down some beers. :P

GII ATA 34-20 ???]]>
ATA 34 Navigation Sun, 20 Jul 2014 10:52:39 +0000