FAQ ATEQ EFCTB (Elevator Feel Computer Test Box)
The EFCTB has been Designed to support all Boeing aircraft with Elevator Feel Computer and Centring Units including all needed gauges/pumps in one single box.
The EFCTB will simulate airspeed by injecting a regulated air pressure through the pitot probes of the aircraft, then measure and report the hydraulic pressure. That is returned to the two hydraulic actuators of the system in response to this airspeed.
- 1.Getting started
- 2. Power Supply
- 3. Auto test
- 4. AMM
- 5. Measurements Specifications
- 6. Aircraft Equipment
- 7. Kits
- 8. Maintenance Centres
A : The probes used by the EFCTB are those located at the rear of the tail. They are identical (same PN) to the main pitot probe located at the front of the aircraft, which is commonly used and operated by our standard adapter kits.
AÂ :Â RSS stands for Root Square Sum. This is an alternative method to determine the accuracy of an equipment.
You can find additional information on this alternative method on the web. For example you can have a look at this page:Â https://www.fiveflute.com/guide/introduction-to-root-sum-squared-rss-tolerance-analysis/
A: In the toolbox we have a “standard” power supply, 110/230Vac – 50/60Hz. The onboard AC network of an aircraft is 115Vac/400hz.
The prototype test box, that has been tested on site, does in fact, work on 400Hz aircraft power.
A : EFCTB is called in Task 27-31-67-700-801, related to Boeing 737-700/800 aircrafts.
A : The application requires a safety limitation to a maximum of 6 psi, to avoid over-pressurizing the aircraft system.
That’s why the air regulator is limited to 6 psi, and why we’ve added a 6 psi relief valve.
The pressure gauges available on the market are 10psi gauges. They have their own accuracy, which is a % of their full scale (0-10psi). We must therefore refer to this full scale (0-10psi) when determining accuracy.
A : No. it’s not mentioned within the maintenance task. It should be considered as an internal process that has been requested by our first customer to ensure the device is working correctly. When this auto test is complete and a leak occurs, that means the leak comes from the aircraft system and not from the EFCTB cables.
A : A kit is dedicated to an aircraft:
- Adaptors depend of installed probes
- Seal spare parts depend on provided adaptors
- Hoses’ length is adjusted to probes location and aircraft dimensions
The kit reference also includes the type of power cord.
A : The Elevator Feel Computer is in the vertical stabilizer, above and separate from the APU which is in the bottom of the tail.
A : On Boeing 737, the FEEL DIFF PRESS indication on the flight control panel can illuminate in the following cases:
(The feel system simulates “actual feel forces” at the control column from the hydraulically supported elevator panels)
- The first one is related to a differential of A & B hydraulic pressures to the elevator feel system. When hydraulic system pressure drops > 25% related to the higher pressure, the FEEL DIFF PRESS light illuminates on the flight control panel with a 30 second delay. The 30 second delay prevents the light from “flickering” when pressure drops in either system by a high demand such as gear selection.
- The second is related to the dynamic air pressure supply to the Elevator Feel Computer. It receives dynamic pressure from the two pitot tubes mounted on either side of the vertical stabilizer. When the computer receives an erratic signal, it’d be the same as the pressure drop and the light illuminates. (failed probe heater and icing conditions)
- The third is related to the Stall Management and Yaw Damper (SMYD), and a so-called Elevator Feel Shift module (EFS), which creates a ±4 times higher forward control column force when approaching the stall region. This force uses a reduced system “A” pressure and when this reducer fails, opening prematurely providing a higher-than-normal A system pressure to the feel actuator, the FEEL DIFF PRESS also illuminates after 30 seconds.
Note on the last system, it’s inhibited <100 ft. RA and AP selected, and when the EFS is not operational.
The EFCTB will detect an obstruction or leak in the system’s pneumatic network (2nd failure case described above).
Then, the device will detect a leak in the hydraulic system (1st case of failure described above).
Finally, it will detect any inconsistency in the pressure build-up slopes of the two hydraulic circuits A and B (which may help identify the 3rd failure case described above).
A: Since the visco drains are listed as interchangeable in the IPC the operator can purchase and install either part number. That being the case, there is no way of knowing which drain will be installed on the aircraft being tested.
A : MRO doing C checks or deeper. EFCTB is not required for A/B checks at line stations of airlines. Usually, the customers are MRO centres of airline branches.
Download Technical Data Sheet EFCTB
