Captain Judy’s Corner: The Need for Speed
Going for a world record!
As the Citation approached Kangerlussuaq, Greenland (BGSF), I queried the Air Traffic Controller about their readiness as officiators for my Federation Aeronautique Internationale (FAI), National Aeronautic Association (NAA) World Record Attempt. The controller responded with, “Affirmative.” After landing, two airport officials assured the jet was fueled before giving a friendly wave-off as I taxied to the runway hold lines. We were cleared direct to Reykjavik. In a heavy Danish accent, the final air traffic remarks were, “The Clock is ready for your record-breaker, N178SF!”
Kangerlussuaq, Greenland to Reykjavik, Iceland was a total of 727 nautical miles. I leveled the jet at FL290 (29,000 feet) in clearing skies. As planned and reviewed with my crew, I set the cruise power (Vc) for optimum at ninety-five percent instead of maximum speed cruise power at eighty five percent. The First Officer carefully monitored the Engine Indication Systems (EIS) for any discrepancies while I monitored flight instruments. We were all aware that I was on the clock; I had to beat 2 hours and 30 minutes for a record success.
“We were all aware that I was on the clock; I had to beat 2 hours and 30 minutes for a record success.”
Once on Reykjavik tower, the controllers welcomed us with reassurance that they were ready as the landing official record keepers. Entering the small FBO (office, known as Fixed Base Operator), the tall Danish man greeted me excitedly shaking my hand giving premature congratulations. He exclaimed in a similar Danish accent with, “Congratulations, Captain Judy Rice, you record-breaker!” It seemed all of the Reykjavik crew were elated at being part of my FAI, NAA record. It would be months later before knowing if I were awarded this record.
How is aircraft speed measured compared to a car?
Regardless of record setting, cruising in a jet, or a small training aircraft speed is measured differently compared to a car. A car’s speed is defined as miles per hour (mph) and an aircraft in mph, knots (kts), or Mach. There are different variations on these speeds depending on temperature, wind, and pressure. The airspeed a pilot reads right of the instrument is called indicated airspeed (IAS). Calibrated airspeed (CAS) is indicated airspeed corrected for installation errors of either the pitot tube or static port. The errors must be accountable when IAS does not equal CAS.
What is true airspeed?
True airspeed (TAS) is the speed of the aircraft relative to the air it’s flying through. TAS is greatly affected by high altitude and hot temperature. TAS is higher than IAS because the higher the aircraft flies the fewer air molecules available for the instrument to efficiently measure speed. Temperature also affects TAS because warm air molecules rise quicker than cold air molecules. On a warm day compared to a cooler day, there are fewer air molecules. A pilot must calculate indicated airspeed according to TAS. The high temperatures significantly decrease takeoff and landing performance for the same reasons as a higher altitude. The air is less dense in both situations.
What is groundspeed?
The movement of an airplane relative to the ground is called groundspeed (GS). A headwind would cause a slower GS and a tailwind would cause a faster GS. IAS could read 100kts, but with a tailwind the GS would be faster. A headwind would cause the aircraft to be flying slower with an IAS reading 100kts. A pilot must calculate GS according to winds at the altitude or could possibly miscalculate fuel required.
What is Mach?
Mach is a measurement relative to the speed of sound. Mach 1 averages 666 knots or 767mph. Cruising in a small training aircraft at 110 knots would average 128 mph or Mach 0.16. Commercial jets’ average cruise speeds are about 500 knots, which is 575 mph, or 0.75 Mach. One of the largest passenger jets, the Boeing 777 typically cruises at 560 knots converting to 645 mph, or Mach 0.84. Most jet airspeed indicators automatically change from knots to Mach once reaching a high altitude. The Citation’s Mach conversion altitude was FL300 (30,000 feet).
Student pilots learn the importance of calculating and planning for each type of airspeed. Learning in a slow, training airplane while managing these airspeeds is the foundation throughout their career and vital to the safety of flight.
Have a need for speed? Get checked out in the Lockheed SR-71 Blackbird. The Blackbird holds the world record for the fastest air-breathing manned aircraft with a recorded speed of 1,905.81 knots, which is 2,193.2 mph, or 2.8584 Mach. That is a staggering 37 miles per minute!
At 350 mph, which is 304.15 knots, or .46 Mach, just under 2:24 minutes I was awarded the FAI, NAA Speed Over a Recognized Course from Kangerlussuaq, Greenland to Reykjavik, Iceland.
Read more articles by Captain Judy Rice!