PPRuNe Forums - View Single Post - Jet goes down on its way to Medellin, Colombia
Old 29th Nov 2016, 21:03
  #80 (permalink)  
plhought
 
Join Date: Jun 2014
Location: Canada
Posts: 102
A lot of technical mis-understanding about this airframe so i'll try and summarize some technical tidbits here. Apologies if it appears hap-hazard - just going back through the thread.

- No fuel dumping provisions in the 146/RJ

- Fuel Qty indication is availible with only battery power. Infact, there's a momentary Fuel Qty pushbutton above the Engine Insturments that lets you check qty with battery off. It's a digital display on the bottom of the EIS.

- Pannier tanks can be installed and removed regardless if aircraft was delivered from factory with/without them. I suspect this one did not have any installed though, as it's a relatively big job and usually the entire (relatively small) operator community will get wind of someone looking for pannier tanks parts.

- Pannier(or auxillary) tanks are considered part of the wing tanks and thier qty indication is combined with wing tanks if installed. Also an annunciation if they are not empty on the overhead panel. Pannier tanks will feed into thier respective wing tanks.

- I highly doubt any of the belly aux tanks were installed in this aircraft. They are very rare and the only outfit that I know that uses them consistenly nowadays is the FAAM aircraft. Home

- Redundancy is king on this aircraft (it is British...). As detailed above a bit, electrical power is primarily derived from two 115/200 VAC generators on engines 1 and 4. The APU also drives an identical generator without the CSD. Each single AC generator is capable of completely powering the aircraft. In the Avro RJ, bus switching in the event of a generator failure is automatic (provided panel is configured correctly). There is no paralled AC buses in this aircraft. DC power is provided through two (optional third) Transformer Rectifier Units. 26VAC power through transformers for some avionics.

- Essential and Emergency (different buses on this aircraft) AC & DC power can be provided from: Battery (in conjunction with static inverter), and/or a hydraulically powered standby generator (Powered off green system - requires #3 engine-driven-hydraulic pump functioning. Isolates Green system)

- With emergency DC (battery) and AC (static inverter) only:
- Standby Horizon
- #1 VOR/ILS
- #1 COM
- #1 XPNDR
- Standby ASI and Altimeter (straight old pitot/static insturments - no DC draw)
- *I think* L/H landing light
- Pilot's Windshield wiper
- Yellow system DC pump (used to help extend yellow emergency extension jack on main gear, and pump up brake accumulator)
- Anti-skid (Anti-Skid sys. switch has to be placed in BATT position)
- EIS N2 indication
- EIS EGT indication
- FADEC continues to function (if engines are) through PMA's on the FADEC/HMU units on engines.

With Essential AC & DC (from Green system hydraulic stand-by generator)
- couple more engine indications
- More avionics
- normal cockpit lighting
- Battery is isolated w/ standby generator operating.

- Fuel system is a mix of complexity and simplicity.


Anhedral wings will make fuel in the wing tanks go outboard through gravity. Gravity & jet transfer pumps flow fuel from wing tanks to Inboard and Outboard feed tanks in each wing. Inboard for #2/3 engine - Outboard for #1/4. AC pumps in each feed tank provide jet-transfer pump pressure and pressure fuel to engines. Engines will suction-feed fine from feed-tanks though as well.
Center-tank fuel will flow into wing tanks. Floats in each feed tank will annuciate a low fuel condition if any tank is less than full (~600 lbs each).

- In the event of an AC electrical failure, standby hydraulically driven fuel pumps can provide fuel pressure.

- Primary flight controls with exception of rudder are completely manual with flying/servo tabs.
- Loss of yellow hydraulics means no roll spoilers, and some ground spoilers
- Loss of green means no speed-brake, other ground spoilers, and primary gear extension.
- Flaps can run half-speed off a single (yellow or green) hydraulic system.
- Alternate gear extention is gravity, with an emergency-yellow assister-jack for the main gear that may be powered from Yellow DC pump.

It is typical operator method to have APU running below 10,000 ft, providing bleed air for AC packs and pressurization. Frees up bleed air from the anemic engines (LF507). The APU Gen switch will usually be left on, although it will not be on either bus. In event of Gen failure with APU Gen on, APU gen will power the failed bus. APU running does jump into your fuel usage a bit though too...

Having said all this.....this redundancy is very suspect when you have no fuel....
plhought is offline