Tips from the Pros - March 2012
Monday, February 27, 2012 at 1:38PM
Webmaster in Tips from the Pros, business aviation, flight instruction, flight tips, flying a jet, general aviaiton, jet, jet flight, pilot, turbine aircraft

Upgrading to Jets

By Mitchell Ange

President, Arizona Type Ratings

More and more, we see private owners of light jets deciding to upgrade their personal flying skills and obtain the training and ratings needed to operate their jet aircraft personally. Doing so allows them to lower operating cost and enhance schedule flexibility.  But, what is it like to move up to these high performance, turbine aircraft.  Let’s take a quick look at speed control.

One jet characteristic that takes getting used to is the amount of thrust lever movement required to effect a significant airspeed change. Pilots transitioning from anything with propellers, whether piston or turbine powered, are accustomed to gently “tweaking” thrust levers, with the correct expectation of being rewarded with a rapid response. This gentle thrust lever movement makes the flying experience in propeller-driven airplanes smooth and comfortable. In turbocharged piston-powered aircraft, being smooth with power changes is desirable from a maintenance point of view as well, reducing shock-cooling concerns. In addition, the cabin altitude of many pressurized piston aircraft responds uncomfortably to brisk thrust lever movement. None of these “comfort” concerns apply to small, modern, civilian jets. But speed changes in a jet may require significant movement of the thrust levers.  Fortunately resulting acceleration or deceleration will be gentle and comfortable.  Don’t be afraid to aggressively move the thrust levers on a small jet, nothing bad will happen.

Power changes result in other “jet peculiar” phenomena. Jets will frequently accelerate and decelerate for a significant period of time after thrust changes are made. When you add or reduce thrust, a gentle change in airspeed will commence that may continue for several minutes. This is not a bad thing; it’s just something you will need to monitor. This characteristic, plus the fact that many jets don’t sound or feel much different at 150 kts than at 250 kts, can result in the airplane getting very slow or fast, undetected. You can’t rely on sound or feel as indicators of airspeed, as you may have been able to in your propeller driven aircraft. You will need to monitor the airspeed indicator religiously while getting accustomed to these airplanes. You will typically be provided with some “target power settings” to help you deal with these characteristics. These thrust settings are expressed either in pounds-per-hour fuel burn or in N1 percent rpm. Regardless of the index used, memorizing these numbers will greatly simplify your energy management task.

Since the “rotary speed brakes” offered by propellers are missing on pure turbojet engines, you can pick up a lot of speed in the descent. Free airspeed while descending in the en route environment is not a problem as long as aircraft speed limitations or ATC speed restrictions are not exceeded. In the terminal and approach environments however, excess airspeed can become a problem. We suggest you always have a target airspeed in mind and make the airplane fly that airspeed. Consequently, “flight idle” thrust will frequently be suggested during step-downs on approaches in order to prevent undesirable increases in airspeed. And keep in mind that you will then need to return thrust levers to that target power setting after leveling off to prevent the airplane from getting too slow. Again, get comfortable moving thrust levers more often and more aggressively in these light jets.

A new term will present itself as you transition from light propeller driven aircraft to the light jet – that being “V-Speeds.” There are many of them but only a few are applicable to routine jet operations. Approximations of some of these “V-Speeds” are frequently presented on the airspeed indicator of most light twins, but these colorful markings are at a given weight, temperature and altitude. In jets, these speeds are precisely computed under current, existing conditions and referred to during takeoff and landing.

Let’s look at V1 (sometimes called “decision speed”), the speed after which takeoff should be continued in the event of an abnormality during the takeoff roll. At V1, your right hand should be moved from the thrust levers to the yoke, as we are going flying. V1 is provided by the manufacturer and will vary with altitude, temperature and weight.  Consult charts in the Normal Procedures Checklist and Aircraft Flight Manual (AFM) and set the airspeed “bug” on the copilot’s airspeed indicator if operating crew, and on the captain’s airspeed indicator if operating single pilot. With an Electronic Flight Information System (EFIS) equipped jet, this airspeed index will appear on both the pilot’s and copilot’s airspeed indicators. You might ask, “Why not stop the airplane if I still have useable runway ahead of me?” Statistically, high-speed aborted takeoffs are very dangerous. Tire traction, directional control and predictable braking action are poor. At V1, speed is adequate to safely fly the airplane and return to the departing airport or some other airport if desired. Again, we are committed to fly at V1.

Closely following V1 is Vr (rotate speed). Frequently, V1 and Vr may even be the same speed. If you rotate to the published initial pitch angle at Vr, the airplane will climb through 35 feet above the runway, with one engine not operating, within your published takeoff distance. In the vast majority of departures, you will have several times this published takeoff distance available and fortunately both engines are running. Consequently, we frequently rotate at Vr plus a few knots as a “long runway” procedure. This improves overall performance and handling.

V2 follows Vr, which is of consequence to us only in the event of an engine failure after V1. V2 is normally “bug’d” on the captain’s airspeed indicator and should be maintained after gear retraction. V2 is similar to best angle of climb speed with one engine inoperative. V2 should be flown to the altitude specified in the AFM, typically either 400 or 1,500 feet AGL. Upon reaching the specified altitude, the pitch angle should be reduced as is necessary to accelerate the aircraft without descending. As you accelerate through V2+10 kts, departure flaps are to be retracted. The last departure V speed to be targeted is Venr or Vyse. This speed is similar to best rate of climb speed with one engine inoperative. This speed would be flown if further single engine climb is required.

Two approach “V” speeds come into play, Vref and possibly Vapp. These speeds are a function of weight only. Vref is 1.3 stall speed in landing configuration and Vapp is 1.3 stall speed in the approach flaps configuration. This assumes we are not maneuvering the airplane and wings are level. These are minimum “approaching the threshold” speeds. Typical target speeds will be significantly higher away from the airport. 

Flying the light jet is not that different from flying a light piston or turboprop twin, and completely within the skill capabilities of a well trained private owner. Approach speeds are similar and there are few operational differences. Be prepared to move thrust levers more aggressively, be aware of airspeed trends and know your power settings. Have a target airspeed in mind. Be prepared to set and fly specific airspeeds that apply precisely to current conditions. Finally, the right hand does not stay on the throttles until there is no useable runway left, as is the case in the light twin. Anything you do to the thrust levers after V1 will be wrong, so remove your hand and remove the temptation. On this class of airplane, we are going flying at V1.

 

 

 

 

 

 

 

 

Article originally appeared on In Flight USA (http://www.inflightusa.com/).
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