Central Flying Academy Cruise Climb Speed
What Is Cruise Climb Speed, And When Should You Use It?
If Vx is your best angle of climb (used to reach an altitude in the shortest lateral distance) and Vy is your best rate of climb (used to reach an altitude in the shortest amount of time), then what exactly is Vcc, or cruise climb speed?
Vcc is commonly called "enroute climb speed", and it's always faster than Vy. Unless a steep climb is required to avoid terrain or to fly a departure procedure, cruise climb speeds allow you to fly faster, with a relatively small loss of climb performance.
So what aircraft have a cruise climb speed, and what types of aircraft benefit most from it? We'll get to that in a bit, but first...
Benefits of flying Vcc
Cruise climb helps you in three ways. First, increased airflow keeps your engine cooler in the climb. That's especially important for high performance piston aircraft.
Second, cruise climb gets you to your destination faster. You do lose some climb performance, but in most aircraft, it's an acceptable (and sometimes almost imperceivable) loss of climb performance, in exchange for faster forward airspeed in the climb.
And finally, you get better forward visibility in a cruise climb. After all, you're supposed to be looking out the window for traffic. Plus, a reduced pitch attitude can make your passengers feel more relaxed. If you're flying an unpressurized aircraft, the reduced rate of climb can also help mitigate pressure changes that your passengers experience. Remember this tip if you have a sick passenger, young child, or baby on board.
When Is A Cruise Climb speed Published?
It depends on the plane, but in general, the higher the performance, the more likely you are to have a published cruise climb speed.
But even the Cessna 172S has a recommendation for cruise climbs. The 172's sea-level Vy is published at 74 knots. Enroute climb (Vcc) is published at 75-85 knots. Here's a quote from the POH...
"Normal enroute climbs are performed with flaps up and full throttle and at speeds 5 to 10 knots higher than best rate-of-climb speeds for the best combination of performance, visibility, and engine cooling."
An Easy Rule-of-Thumb If You Don't Have A Published Vcc
If you want to figure out the cruise climb speed for your airplane, and you don't have a published speed, a good rule-of-thumb is to find the difference between Vx and Vy, and add that number to Vy.
For example, a POH for the Piper Warrior III has a Vy of 79 knots and a Vx of 63 knots. Add the difference of 16 knots to Vy, and you can estimate cruise climb speed to be around 95 knots. Depending on weight and performance, 95 knots might be a little on the high side, but it's a good ballpark to start with. It also gives you a speed you can start experimenting with in the climb.
How Exactly Does Performance Change?
To analyze the change of performance, let's look at a POH that has both rates published: the Cessna 208EX Caravan. While the Caravan might be different than what you fly, the performance change is actually very similar in most single-engine aircraft.
Let's look at climb rates first. Here are the conditions: 8,000 foot pressure altitude, 20 degrees Celsius, maximum takeoff weight of 8,807 pounds.
- Vy (102 knots): 740 feet per minute
- Vcc (115 knots): 675 feet per minute
With this scenario, you only lose 65 feet-per-minute climb rate, in exchange for 13 knots more airspeed. That equates to 12% more speed, for an 8% loss of FPM.
What about time, fuel, and distance for climb? Here are the conditions: climb from sea level to 8,000 feet, standard temperature, and maximum weight.
- Vy: 7 minutes, 61 pounds of fuel, and 13 nautical miles
- Vcc: 7 minutes, 62 pounds of fuel, and 14 nautical miles
In this example, the time to climb is essentially the same, you'll only burn about 2% more fuel, and you'll have over 7% faster forward airspeed.
While this example was limited to the Cessna Caravan, in most airplanes you'll find that the percentage change in FPM is relatively small in comparison to the substantially better airspeed flown at cruise climb.
A Cooler, Faster Climb Speed
If you have the capability to fly a cruise climb departure, you can shave time off your trip, keep your engine in better shape, and make your passengers in the back more comfortable.
This is not an original article. It first appeared on boldmethod.com on 5 December 2017. To read the original article click here.
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