Altimeter and airspeed testers

Citation

(2002), "Altimeter and airspeed testers", Aircraft Engineering and Aerospace Technology, Vol. 74 No. 1. https://doi.org/10.1108/aeat.2002.12774aad.013

Altimeter and airspeed testers

Keywords: Aircraft, Microprocessors

Two new microprocessor based test instruments for aircraft systems are available from Labcell Ltd., Hook, Hampshire, UK. The Meriam Model 353 precision altimeter tester claims switchable altitude, rate of climb and static system leak rate testing, while the Meriam Model 354 precision airspeed tester provides both accurate airspeed indication and pitot tube leak test capability. Both instruments are calibrated to traceable NIST standards (Plate 5).

Plate 5 Two new microprocessor based test instruments for aircraft systems are available from Labcell Ltd., Hook, Hampshire. The Meriam Model 353 precision altimeter tester offers switchable altitude, rate of climb and static system leak rate testing, while the Meriam Model 354 precision airspeed tester provides both accurate airspeed indication and pitot tube leak test capability. Both instruments are calibrated to traceable NIST standards

Instrumentation of this type is vital to ensure that aircrew gain accurate data from their onboard instruments. As the skies become busier, with reduced vertical separation of airways, accurate altitude information has become essential.

The Model 353 altimeter tester has been designed to calibrate to an accuracy Of ±0.02 per cent FS, where FS is equivalent to 90 mm of mercury absolute barometric pressure. This reportedly translates into accuracy of ±7 feet at seal level, ±38 feet at 36000 feet, and ±70 feet at 60000 feet, exceeding FAR 43 Appendix E requirements. Working range of the instrument is stated to be -200 to +60000 feet. It can also be used to assess rate of climb at rates up to ±6000 feet per minute.

Compact design, ease of use, accuracy and reliability are said to be key features of the instrument's design. Program selection is via four keys which, among other things, allow field re-zero of the sensor using sea level barometric pressure, elevation above sea level and ambient temperature. Measuring resolution is to the nearest foot or meter, and the instrument can also be stitched to display a variety of pressure units.

The Type 354 precision airspeed tester is similar in appearance and provides a range of capabilities to complement those of the Type 353. Airspeed up to 514 knots/200 inches of water can be displayed in a variety of units (knots, mph, kph), to accuracy of ±0.05 per cent of full scale. Display resolution is 0.1 knots/mph/kph). Leak rate test capability is available with this instrument as is a re- zeroing procedure, the latter subject to both pitot and static ports being vented.

Both instruments are powered by a 9 volt alkaline battery, have ABS plastic casings and are suitable for operational use at ambient temperatures between 23°F and 122°F. Both instruments feature 45 minute automatic shutoff which may be disabled by the user if required.

Details available from: Labcell Ltd, Tel: +44 (0)1256 760777; Fax: +44 (00 1256 760921