L-1011 Engine: Vibration Indication

To measure the RB.211 engine vibration several sensors are used to feed the indicator systems on the L-1011.

Vibration Pickups

• Two pickups utilized
• Both pickups located on top of IP compressor case
• The pickups are identified as A and B
• The pickups provide signals for the signal conditioner unit

Signal Conditioner

• Contains rectifiers and filters for processing signals from pickups. 
• Contains level detector which operates warning light on respective engine indicator
• Provides three frequency bands that correspond to vibration frequencies of the N1, N2 and N3 stages.

Avioncis Bending: Vibration Indicator - Pinout

Here is the pinout for the Lockheed L-1011 Vibration Instrument. It is a rather simple pointer instrument that can be driven quite easily with just a few external components. Below is a rough picture of what the instrument looks inside. Here are the key functions:

a) Test switch drives the needle to the 12 o'clock position .... or 2.5 on the vibration indicator.
b) Test switch also illuminates the vibration warning light.

Click the image below for better resolution.


Pinout of the 12 pin connector:

1 - 5V AC Instrument Illumination
2 - 5V AC Instrument Illumination
3 - Instrument Casing Ground
4 - 12V Test Input for Indicator
5 - Vibration Signal (TP)
6 - 28V Test Input for Annunciator
7 - Vibration Signal (TP)
8 - Annunciator GND
9 - Annunciator Input
10 - Not Used
11 - Not Used
12 - Not Used


The signal for the vibration indicator requires an external resistor and can be driven with DC or a differential signal.

System Description by Don Pierce: Engine Status and Engine Oil

ENGINE STATUS Panel:

The top row of indicators are the N2 indicators, showing N2 speed. They are round dial instruments on all L-1011s, even though some planes have vertical tape instruments for N1 and N3. It is normal for the FE to call out beginning of N2 rotation during the engine start process.


The second row if indicators are the Vibration Monitor Indicators. They read from 0 to 5 units of vibration. Each indicator has a BITE button which will drive that respective indicator to approximately 4.0 units, verifying indicator operation. Also. each indicator has an amber light that illuminates about about half-scale (2.5 units) At the same time a light will illuminate on the pilots' caution and warning panel. The reading of the light varies - it might be ENG VIB/FLTR PRESS or ENGINE/APU STATUS.

Below the indicators are a series of test-related switches. The TEST push-button switch is used to test the signal conditioner (located in the MESC) and all three indicators. Pressing and holding the switch will cause all three indicators to read approximately 4.0 units; the amber lights will illuminate when the needles of the indicators pass about 2.5 units. When the switch is release, the indicator will return to 0 units (assuming the engine is not running) but the light remains "on", if the needles had passed 3.0 units when the needle was "rising". To extinguish the lights, the TEST switch must be pressed a second time (briefly).

The A and B latching switchlights provide the capability to select either of the two vibration pickups. When both switchlights are unlatched, both pickups are sampled, every 0.5 second. Note: the reading for the switchlights may be FAN and TRUB - for an earlier configuration; location of the vibration transducers will also vary. The ON light is switchlight position.

The four-position rotary switch is a "filter selector". When the switch is at the NORM (normal) position, the rotor frequency being monitored is the frequency range of all three rotating assemblies. When the other three rotary switch positions are selected, the frequency range is of one of the three rotors being monitored: LOW is the LP shaft (N1), MED is the IP shaft (N2) and HIGH is the HP shaft (N3). Note: The level of vibration being seen depends on the "age" of the engine.


ENGINE OIL Panel:

The engine oil QUANTITY indicators have a units display that varies from airline to airline; the quantity also varies, depending on type of engine.

Below the QUANTITY indicators are three oil TEMP indicators, in °C. All six of these indicators each have a small BITE button that is used to test the respective indicator. Faceplate light access for all six indicators is via the front of the indicator. All six instruments are made by General Electric.

Next are three oil PRESS (pressure) gages, manufactured by Smiths Industries. The range of the gage is 0 to 100 psi, in increments of 5 psi. The range is red from 0 to 35 psi, then yellow from 35 to 40, and green from 40 to 100 psi. The three pressure gages have a single, common TEST switchlight. There are three OIL PRESS ENG (x) lights on the pilots' caution and warning panel, which illuminate when the associated engine's oil pressure is too low.

The three amber FILTER PRESSURE lights illuminate to show an excessive pressure drop across either the associated oil pressure filter or the associated fine oil scavenge filter. At the same time, the ENG VIB/FLTR PRESS light on the caution and warning panel will illuminate. This light was also discussed (above) along with Engine Vibration.