Topics in Category: Hawker - Rotate.Aero Wed, 15 Aug 2018 18:29:23 +0000 MYOB /media/kunena/images/icons/rss.png Topics in Category: Hawker - Rotate.Aero en-gb ATA 25-10, Instrument Cooling - by: Mark

With the multifunction displays removed, there was a large amount of air coming from the piccolo tube located below the display racks.

With the lower side-wall pulled off, it could be seen that the air from the cooling fan was split into three user systems. The large tube going to an adjustable vent for the crew (L/H vent), the mid-sized tube going to the multifunction displays, and the small tube routed to the glare-shield.

The weird issue with this particular failure was that the fan output was strong. We could clear the failure by just opening up the crew adjustable vent. With the vent closed, the failure would reappear. Corresponding air flow from both the other outlets would increase with the pilot vent closed. All functions seemed perfectly normal.

The flow sensor is actually part of the fan assembly. It doesn't sense air flow, it senses fan speed. With our one vent closed, the flow was restricted enough to slow the fan down and set off the warning. The funny thing was, the air flow from the failed system was twice as strong as the R/H side which had no failures at all.

The fan assembly is below the floor, just outboard of the control yoke column.

Fan (only the sensor wiring can be seen from this angle).

Hawker 900XP WDM 25-10-12-01]]>
ATA 25 - Equipment/Furnishings Mon, 06 Aug 2018 23:32:41 +0000
ATA 32-60, H125-700 Gear Indiction Breaker Popping - by: Mark

ATA 32 Landing Gear Tue, 14 Apr 2015 22:16:18 +0000
Terminal Strips and Relays - by: Mark
I am dealing with a capt's hand microphone problem. The print led me to look for some relays. I was quite surprised to open the right side wall behind the cockpit to find this...

How smart.... Locate all your relays and a majority of terminal strips in one central location. I don't recall anything like this on the -400 series or the -800 series. Someone can correct me if I'm wrong with that last statement.

The relays I was concerned with were the smaller black ones on the top row. It's interesting (and somewhat confusing) has to how the communication system audio input is accomplished on this aircraft.]]>
General Tue, 25 Nov 2014 00:16:34 +0000
ATA 30, Hawker Window Heat - by: Mark
A/C power is usually supplied in one of two fashions. Either current is “pulsated” on and off or constantly applied with a varying voltage.

Hawker aircraft use the pulsating method. Three phase power from the alternators is supplied directly to the window heating elements. Longer bursts are needed for initial heat and then the duration tapers off as the window temperature comes up.

Three thermisters (sensors) are used for control and overheat shutdown. Hawker sensors are Negative Temperature Coefficient thermisters. NTC sensors resistance decreases as temperature increases.

Hawker windows have three heating elements per window, each connected to one phase of A/C power. Each section has its own sensor. The three sections should receive the same amount of power and the resistance readings of the sensors should be fairly close at all times.

In normal operation, the overheat relay contacts are closed and the control relay cycles to pulsate power to the window. If either overheat sensor’s resistance value falls below a set norm, the overheat relay will open. A warning annunciator will also alert the crew for any overheat problem.

(I recently had a problem with a window overheating approximately 5 minutes after power application. The problem turned out to be an open heating element for the section that had the control sensor. The sensor would never show a resistance change and power remained applied until the overheat sensors shut it down.)

ATA 30 Ice/Rain Protection Mon, 04 Aug 2014 03:45:04 +0000