ADC

[stancioiu]

HI!
Is the airspeed calculated from an air data computer calibrated airspeed or is it still indicated air speed?

[flyboyike]

ADC gives us TAS.

[Empty Cruise]

...can derive TAS but indicates CAS, methinks

[Mad (Flt) Scientist]

Pedantically, if there is an airspeed being indicated to the pilot, that is "Indicated Airspeed".

However, the (unrealised) goal of every Air Data System (including the ADC as a component) to to present a value to the pilot which is as free from error as possible. Therefore, for a 'good' system, it will often be stated that the displayed term is 'Calibrated Airspeed', but this is more a statement of a design objective than a perfectly factual statement.

While Air Data Systems are entirely capable of calculating other airspeeds (such as EAS or TAS) these are not the terms usually displayed to the crew as "airspeed" on the "airspeed tape", even if they may be available through various display options on other pages of a display system.

[hawk37]

Originally Posted by Mad (Flt) Scientist

Therefore, for a 'good' system, it will often be stated that the displayed term is 'Calibrated Airspeed'

MFS, does a "good" systems also have an AFM that gives the pilot speeds in KCAS, ie with static position error already factored in? For example, a holding speed, or an approach speed. The only data I've seen is for business jets and always in KIAS. If an afm stated displayed speeds were CAS, then someone, somewhere, would have to apply a correction

Hawk

[Mad (Flt) Scientist]

I should say that unless it's unequivically stated in an 'approved' document somewhere that the displays are CAS, then the approved speeds are IAS and the displays are IAS.

Even on our aircraft where the displayed speed is within a knot of CAS, we call the various scheduled speeds "IAS".

What I meant was that the ADC vendor will probably say something like "XYZ Inc's whizz-bang ADC displays CAS, altitude and the phone number for the cute pax in 3A" in their sales brochure.

[captjns]

The guzzinta to the ADC are Bernoullies and the goesoutta from the ADC are googoofonics electrons which goes to an amplifier that powers the ASI which is to be as close to CAS as possible.