I believe we all have heard the term stabilized approach. But what is a stabilized approach and why should you practice it?
One of the many aspects that makes the King Air appealing is that it is a forgiving airplane. This makes it a great platform to transition into from a slower, nonpressurized, reciprocating aircraft. Once experience is gained and we are comfortable in the King Air, we can sometimes push the limits of what the airplane can do.
For example, when the controller asks us, “King Air XYZ, can you make a short approach to runway xx?” Too often we find ourselves complying by performing a very close in base-to-final, with a 45-degree bank angle and high sink rate. In a turboprop airplane, the pilot can pull the power levers to idle at any time without concern for cooling the engine too rapidly. Consequently, rapid descents with the propellers in low pitch can be dramatically steep. The King Air is so forgiving that you may be able to get away with this maneuver. This can be fun; however, it is reducing our buffer of safety significantly. If it results in a successful landing, it will reward unsafe behavior.
What do I mean by buffer of safety?
Think of a target that represents safety, where the center of the target is the highest level of safety. As you move toward the outer rings, your safety level decreases until you are outside the target resulting in an accident or incident. Our goal is to be as close to the center of the target as possible (See Figure 1). This will give us the biggest buffer of safety. If something goes wrong, we will have that buffer to fix it. If we are already operating near the edge of the target and something goes wrong, then we fall off the target and end up with an incident or accident (See Figure 2).
On Jan. 4, 2020, a King Air B200 was making an approach in instrument conditions at the Morristown, New Jersey, airport. The pilot reported that he saw an area of patchy fog over the approach end of the runway and leveled off to avoid the fog. He landed the airplane with about 3,000 feet of the nearly 6,000-foot-long runway remaining and felt the airplane hydroplaning while using a combination of wheel braking and the beta range of the propellers. The airplane subsequently overran the end of the runway onto grass and mud, causing the nose landing gear to collapse. The airplane sustained substantial damage to the forward fuselage.
Why was the pilot unable to stop in 3,000 feet? Stopping a King Air B200 in 3,000 feet should not be too difficult. Let’s say the pilot was on speed and descending normally on the approach. We don’t know what altitude the pilot leveled off. If the approach is flown to minimums and the runway is not in sight, the pilot needs to go around. By leveling off at some point then diving for the runway when it came into sight, the airspeed may have increased to a higher-than-normal approach speed. It is also possible that the decent rate was higher than normal. The pilot is no longer in the center of the safety target and has moved closer to the edge.
But all is well, right? The King Air is a forgiving airplane. The pilot is thinking, “I can stop this airplane in 3,000 feet.” Fast and max braking is used as the airplane touches down. The standing water, which was not accounted for, causes the event to go outside the edge of the safety target. The pilot has lost the buffer of safety, resulting in a runway overrun.
How do we stay near the center of the safety target?
We have all heard the saying, “A good approach makes for a good landing.” A stabilized approach is a way to mitigate risks during the landing phase of flight. These risks could potentially result in a runway excursion, loss of control or collision with terrain. Following stabilized approach procedures, FAA best practices and aircraft checklists will keep us in the center of the target of safety, giving us a buffer for fixing excursions. This lowers our overall risk.
According to Chapter 9 of the FAA’s Airplane Flying Handbook, there are seven elements of a stabilized approach.
Glide path
Typically a constant 3 degrees to the touchdown zone on the runway (obstructions permitting).
Heading
The aircraft tracks the centerline to the runway with only minor heading/pitch changes necessary to correct for wind or turbulence to maintain alignment. Bank angle normally limited to 15 degrees once established on final.
Airspeed
The aircraft speed is within +10 /-5 knots indicated airspeed of the recommended landing speed specified in the airplane flight manual, 1.3 Vso or on approved placards/markings. If the pilot applies a gust factor, indicated airspeed should not decay below the recommended landing speed.
Configuration
The aircraft is in the correct landing configuration with flaps as required; landing gear extended and is in trim.
Descent rate
A descent rate (generally 500-1,000 feet per minute for light general aviation aircraft) makes for a safe approach. Minimal adjustments to the descent rate as the airplane approaches the runway provide an additional indication of a stabilized and safe approach. If using a descent rate in excess of 500 fpm due to approach considerations, the pilot should reduce the descent rate prior to 300 feet AGL.
Power setting
The pilot should use a power setting appropriate for the aircraft configuration and not below the minimum power for approach as defined by the AFM.
Briefings and checklists
Completing all briefings and checklists prior to initiating the approach (except the landing checklist) ensures the pilot can focus on the elements listed above.
If the approach is no longer within the stabilized approach criteria, a go-around should be initiated.
I’m sure the pilot of the B200 accident aircraft mentioned earlier in this article would have gladly traded the overrun for a go-around.
What is a best practice when facing an unstable approach?
According to Advisory Circular 91-79B, paragraph 5.2.1 – Unstabilized Approach: Deviations in airspeed, altitude, descent rate, glideslope, runway aim point and localizer control place pilots in a position where recovery to the desired flight path is unlikely. It is the pilot’s responsibility to inform ATC when compliance with an instruction will result in an unstabilized approach.
Going back to our earlier example when the controller asks, “King Air XYZ, can you make a short approach to runway xx?” The best practice would be to reply, “Unable, we will need to continue downwind.”
I can hear the grumblings of some King Air pilots after reading that last sentence. The controller may not be happy with your response, and you are not getting a shortcut to land early. However, you have now reduced your overall risk for that approach. If more King Air pilots said no to the types of requests that would result in an unstable approach, the controllers would be less likely to issue those requests. The controllers don’t push the airliners into an unstable approach because those pilots say “unable.”
We all know that the King Air can do some amazing things. Every time we make a successful landing that is not a result of a stabilized approach, it feels rewarding, making it seem like unstable approaches are fun, normal and not a problem. Not as obvious is the fact that an unstabilized approach is taking us closer to the edge of the safety target. We now have less of a buffer for recovery if something unforeseen happens that may result in an incident or accident. We can limit our overall risk if we practice stabilized approaches.