Does an Aircraft need at least one mechanical Instrument?

  caccy 15:46 25 Mar 15

In this complex computer age should aircraft be fitted with a mechanical,totally independent of any aircraft power or system, "left/right; up/down" indicator? i.e. an instrument on a gimbal.

I seem to remember flying in a glider many years ago that had two vertical tubes with different coloured liquids in them that told you whether you were climbing or decending.

  john bunyan 17:11 25 Mar 15

I seem to remember being given a ride in a friend's Tiger Moth in the early '60's and it had only a compass and an altimeter..

  Forum Editor 18:27 25 Mar 15


I'm not sure what your point is - why would a mechanical "left/right; up/down" indicator be of help?

I assume your thread was in some way prompted by the Alps air crash, but I can't work out how. I'm not aware that so far there has been any suggestion of an instrument systems malfunction.

  Forum Editor 18:33 25 Mar 15

john bunyan

No air speed indicator, Rev counter, or oil pressure gauge?

It must have been an edge of the seat experience.

  john bunyan 19:02 25 Mar 15

Forum Editor

You are right, it did have an air speed indicator, Rev counter and Oil Pressure gauge, inclinometer and Turn / slip. My memory was a bit rusty. I do remember setting off from Shoreham on a proposed trip to France when the visibility cause us to return, and trying to find Lydd in the fog - just spotted the tower in time for a landing before a fuel shortage.

A bit chilly; once at a RAF base they kindly offered to re fuel - asked how many gallons of petrol. The bowser driver expected an answer in hundreds of gallons rather than the 8 requested...

  morddwyd 19:21 25 Mar 15

"once at a RAF base they kindly offered to re fuel - asked how many gallons of petrol. The bowser driver expected an answer in hundreds of gallons rather than the 8 requested..."

I can remember refueling a Shackleton at a US base.

I connected the hose, walked to the edge of the wing and said "Thirty two hundred imperial p-lease mate" which would normally take a few minutes. "Too late" he said, "You've already got thirty six"!

  hssutton 20:41 25 Mar 15

I've emailed a friend who flies an Airbus 380 regarding your question, unfortunately he's on his way back from Beijing so it will be tomorrow before I get an answer. As the FE I'm a little curious regarding the question. This link will take you a view of the A380 cockpit which appears to show only electronic instumentation.

  hssutton 20:42 25 Mar 15

Damm forgot the link A380 Airbus

  hssutton 19:03 26 Mar 15

My pilot friend has sent me this reply to the OP question.

The instrument he is referring to is known as the Attitude Indicator (AI), Artificial Horizon or Attitude Director Indicator (ADI) depending on the make of aircraft that you fly and is used to let the pilot know his attitude in pitch and roll (i.e. up and down, left and right) with reference to the 'real' horizon. In older aircraft, pre Electronic Flight Instrument System (EFIS) aircraft, with an analog instrumentation, the Attitude Indicator was gyro driven. The gyro is mounted within the instrument with its plane of rotation in the horizontal (Spin axis is vertical) in 2 gimbals so the AI therefore has the freedom of movement in all three planes. In EFIS aircraft, the analog instruments were replaced by computer screens, the most common layout consists of screens called a Primary Flight Display (PFD), a Navigation Display (ND) and then one or two screens making up Engine Warning Display (EWD) and Systems Display (SD) on Airbus aircraft, on Boeing aircraft I think these screens are referred to as EICAS. The PFD combines the AI, airspeed indicator, compass and the vertical speed indicator into one single instrument. On airbus aircraft, the information presented on the PFD comes from the Air Data and inertial Reference system, which has replaced the Gyros of the analog system and comprises of computers and a ring laser gyroscope that is a core enabling technology in the system, and is used together with accelerometers, GPS and other sensors to provide raw data. The primary benefits of a ring laser over older mechanical gyros are that there are no moving parts, it is rugged and lightweight, frictionless and does not resist a change in precession. I hope this answers your question.

  hssutton 10:31 27 Mar 15

Addition to the above post, the Airbus has 3 adrs which are backup systems

  caccy 17:23 27 Mar 15

FE It was only partly due to the recent terrible disaster, it's just that I feel that with evermore complex electronic systems taking control we need to be able to "get back to basics" hence my question. As an example, when I go hill walking I take a GPS and Electronic maps but still take a compass and a hard copy map af the area.
With regards to my question I was thinking more in line of a simple piece of informative instrumentation that is totally independent of aircraft supply or systems so that the pilot can look at it and know that what he is seeing is exactly what the attitude of the aircraft is. Not something that has been processed electronically.

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