Some of the issues new jet pilots must confront fall squarely into the category of “nice problem to have.” Looming large among these is the need to control the airspeed of a machine that is endowed with quite a bit more power relative to its weight than any piston aircraft, and even most turboprops. Between performance and regulatory limits, a jet pilot needs to be much more on top of airspeed than his piston brethren.
It’s usually a pleasant surprise to find, for example, that even the lightest of light jets will quite happily accelerate through redline speed at cruise thrust when leveling off at lower altitudes. In the case of airplanes with particularly high thrust-to-weight ratios, even at the aircraft’s ceiling, cruise thrust may yield a speed over redline. But at least structural limits are clearly marked on the airspeed indicator. More insidious are the regulatory limits of FAR 91.117, which vary with lateral and vertical position.
First off, below 10,000 feet msl, indicated airspeed must be kept below 250 knots. It’s easy to inadvertently exceed this limit during a continuous descent. The descent is typically initiated in the vertical speed mode of the autopilot, and power is reduced to maintain a speed comfortably under redline. For many light jets, that redline can be well over 250 knots, so what was an acceptable descent at 10,100 feet becomes violation-inviting at 9,900 feet. The pilot must have the situational awareness to reduce power well in advance of reaching 10,000 feet, so that as the plane descends through 10,000 feet the speed has decreased sufficiently.
March 2011 AOPA Pilot Turbine Edition
- Turbine Intro from Tom Haines, Editor in Chief
- Mission Ready: American Eurocopter's AStar
- Mentoring Matters: The Need for Less Speed
- System Synopsis: Bleed Air Malfunctions
- Ronnie Morgan: Fear Is No Longer a Factor
- Logbook Entry: Commentary
FAR 91.117 specifies two other speed limits—one when at or below 2,500 feet agl within four nautical miles of a Class C or D airport, and one when flying under Class B airspace. In both situations indicated airspeed must be kept at 200 knots or less. The Class B restriction is a particularly easy trap to fall into, as keeping track of the lateral and vertical boundaries of Class B airspace can be a chore when flying into an unfamiliar area. There is no 200 KIAS limit within Class B airspace, so again, a descending pilot may be perfectly legal at a given altitude, but just 10 feet lower be 50 knots over the speed limit as the airplane pops out of the Class B.
Takeoff represents yet another chance to exceed the 200-KIAS limit. Departing from a Class C or D airport, a pilot is assigned a level-off at 2,000 feet. Most jets can easily exceed 200 KIAS during climb unless the pitch is set uncomfortably high or power is reduced below the climb thrust setting. Given that the airplane often reaches 2,000 feet just as a new frequency or heading is being assigned, it’s easy to see why observing this limit is a struggle for nearly all pilots adjusting to jet flying.
Helpful in this situation is the use of a thrust-commanded climb rate. Using the autopilot’s IAS hold mode to command a speed slightly under 200 knots, the pilot then reduces thrust to maintain a vertical speed of 1,000 feet per minute or less. As the airplane levels off, thrust is further reduced to maintain speed. By decreasing the vertical speed well prior to level-off, there will be more time to react to the airplane’s acceleration, and reduce power accordingly.
Just don’t complain to your piston-flying friends about how hard you need to work to keep the speed down.
Neil Singer is a Master CFI and mentor pilot in Cessna and Embraer light jets.
