Interactive Quiz #7:
Airspeed Indicators

The February 1996 crash of a 757 off the Dominican coast appreas to have been caused by a faulty airspeed indicator. In this quiz, which appears in abbreviated form in the May 1996 issue of IFR magazine, we take a look at ASIs and find out how well you understand these most taken-for-granted of cockpit instruments.

by Paul Bertorelli

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The questions in this Brainteaser quiz are based on the FAA's Instrument Flying Handbook.

Answer the questions as best you can, then click on the "score" button to see your score and read the explanations. If you don't like your score the first time around, you can change some of your answers and resubmit. To get the most out of this quiz, we suggest you keep trying until you get a perfect score.

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1. If the static system were plugged up, how would this affect the airspeed indicator?
a. Probably not at all.
b. The ASI would read high.
c. The ASI would read low.
d. The ASI would become erratic.

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2. FAR 91.411 requires a static system check every 24 calendar months. Technically, this is...
a. ...required only if the aircraft will be flown on an IFR flightplan.
b. ...required for any flight, not just IFR.
c. ...required only for large and turbine aircraft flown under IFR.

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3. In order to be flown under IFR, an aircraft must have an alternate static source for the ASI. True or false?
a. True.
b. False.

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4. If the alternate static source were used with a vent inside the cockpit, you'd normally expect the ASI to read:
a. Higher than normal.
b. Lower than normal.
c. The same as with external static source.

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5. On a cross-continental trip, you're coaxing a wheezing Cessna 172 over the Rockies at 12,000 feet. At that altitude, the indicated stall speed will be:
a. Higher than at sea level.
b. Lower than at sea level.
c. The same as at sea level.

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6. Back to our wheezing 172: In the example above, how would the altitude affect the TAS stall speed?
a. TAS stall would be higher than at sea level.
b. TAS stall would be lower.
c. TAS stall would be the same

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7. Extremely cold temperatures are known to cause altimeter errors but these temperature/density variations DON'T affect the airspeed indicator. True or false?
a. True.
b. False.

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8. You're motoring along on the airway at 10,000 feet when ATC says "descend and maintain 8000 feet." When you pitch over to begin the descent, the airspeed starts going down. What's likely to be the problem?
a. Frozen or plugged static system.
b. Frozen or plugged pitot tube.
c. Both systems frozen or plugged.
d. A ripple in the space-time continuum.

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9. In question six, we asked about indicated stall speeds and altitude. In truth, airspeed indications really aren't very accurate at high angles of attack because...
a. ...pitot tube position error.
b. ...static source error.
c. ...both pitot and static errors, with most the errors due to static port position.

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10. BONUS QUESTION: What's the difference between indicated airspeed and equivalent airspeed.
a. Indicated is what you read, equivalent is corrected for pressure and position errors.
b. Equivalent is true airspeed corrected for position errors.
c. Equivalent airspeed is calibrated airspeed corrected for compressibility effects.

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