More About Climbs and Descents

Climbs and descents are affected by forces in flight. Anytime an airplane is unaccelerated in flight while maintaining a constant airspeed and path, then the for aerodynamic forces of flight (thrust, drag, lift, weight) are in equilibrium.

In unaccelerated flight, the force of weight is equal to the force of lift and the force of drag is equal to the force of thrust.

While most commonly thought of as being in true level flight, these four forces can also be in equilibrium in climbs and descents.

Going from Straight and Level to a Climb

Before starting the climb, you will want to make sure the mixture is in the full rich position. Next, turn on the landing lights which will increase visibility to assist in collision avoidance.

If climbing 200 feet or greater, increase the poser by pushing in the throttle to full power (full rich). Since you will be adding additional power. right rudder may need to be added to counteract yaw.

Apply back pressure to the control wheel to pitch the front of the nose to around 10 degrees above level flight.

Make sure to monitor the climb to ensure no turning, sideways or leaning sensation which can also be visible in the slip/skid indicator.

If the indicator is to the right, more right rudder will be needed and if to the left, more left rudder will be needed.

Airspeed while climbing

If the airspeed is too low while climbing, slightly pitch the nose down and adjust the trim as necessary.

If the airspeed is too fast, pitch the aircraft up slightly and adjust the trim as necessary.

Getting back to Straight and Level

When are are approaching your desired altitude, you want to begin your level off at approximately 10% of the vertical climb rate so as an example, if you are climbing at 500 feet/minute, you would start to level off at 50 feet prior to your desired elevation.

When reaching your altitude, you will need to ease the nose down to a level flight altitude while leaving the power setting at climb and letting the airspeed build back up to the desired cruise speed. As airspeed increases, the nose will tend to pitch up so it will be necessary to hold the nose at the level altitude by applying forward pressure to the control wheel.

Once you have reached your desired cruise speed, adjust the throttle to the desired RPM setting for cruise and trim as necessary.

Now that the engine is not running full power, the mixture can be adjusted as needed with a lean mixture for cruising above 3000 ft mean seal level or richened if doing maneuvers below 3000 feet below MSL.

From Straight and Level to Descending

When descending more than 200 feet, reduce power to approximately 1500-1800 RPM

The descent rate for smaller airplane is usually around 400-500 feet per minute.

For a slower rate of descent, you can use a higherRPM (2000) settings as this will increase the speed.

For a faster rate of descent, you can lower the RPM (1500) which will reduce the power, however is is important not to descent for an extended period of time with the engine at idle to avoid rapidly cooling the engine which could cause a build up of carburetor ice.

In order to ensure not to yaw on the descent, you may need to use some left rudder pedal to offset the forces.

just as you started your climb level off at 10%, the same goes for the level off from descent. Use the same 10% ratio to get back to cruise altitude.

When reaching your cruise altitude from descent, you will need to add back pressure to the control wheel to raise the nose to a level flight attitude. Since you previously decreased the RPM, you will now need to raise the RPM  by pushing in the throttle to gain speed then trim as necessary. Adjust mixture as necessary and just as before, a lean mixture if cruising above 3000 ft MSL and richened mixture if performing maneuvers below 3000 MSL.

Additional Tips

Adjust the throttle if climbing or descending more than 200 feet.

If the climb or descent is less than around 200 feet, make a slow climb/descent using the control wheel only as adjusting the throttle can greatly increase the climb/descent rate and cause you to miss your desired altitude.

Power-Off Descent

There are two forms of drag that have an affect on the aircraft.

Induced Drag – This is a result from the production of lift.

Induced drag varies inversely with airspeed in that as airspeed increases, the induced drag will decrease and as airspeed decreases, induced drag will increase.

Parasite Drag – This results from the airplane moving through the air.

Parasite drag varies directly with airspeed in that as airspeed increases, parasite drag increases and as speed decreases, parasite drag decreases.

Induced Drag + Parasite Drag = Total Drag

The Best Glide Speed

Best Glide Speed” – The greatest distance an aircraft will glide with the at a specific airspeed for the total weight with the power off. The “best glide speed” is shown in the Pilots Operating Handbook (POH) and is often given at maximum gross weight.

Best glide speed is the airspeed where the total drag is the least (lowest point on the total drag curve).

Best glide speed is the point with the highest ratio of lift to drag.

On the G1000 primary flight display, this is indicated with a “G” and it is not marked on analog airspeed indicators.

The “Best Glide Speed” should be included in the takeoff briefing so it can be quickly recalled in an emergency keeping in mind that the best glide speed for you airplane varies with the weight. The lighter the aircraft, the slower best glide speed and the heavier the aircraft, the faster best glide speed.

A general rule of thumb is to reduce glide speed by 5% for every 10% below max gross.

A Cessna 172 Skyhawk without power can glide about 9 feet for every foot of altitude lost giving it a glide ratio of about 9 to 1. Translated, this means that for every 1,000 feet above ground, you can glide roughly 9,000 feet over the ground or about 1.5 nautical miles provided there is no wind.

Using flaps which increase drag will result in less glide distance and also flying faster or slower than your best glide speed will result in less glide distance.

The glide speed changes with wait, but the distance does not change as the airplane will glide down the same path regardless of weight. The lift-over-drag ratio is based on the aircraft shape.

Lighter aircraft have to fly slower to get the best glide speed

Glide distance is the same for heavy or lighter airplane but heavy aircraft will have to fly faster and lighter aircraft will have to fly slower. Lighter aircraft will give more time in the descent if there is a problem in flight.