Matthew Waugh
Good approaches make good landings easy and bad approaches make good landings hard and sometimes impossible. In aviation training we preach a lot about go-arounds and how we should always go-around if we’re not comfortable and there’s no shame in a go-around. But truth is most pilots “save” more landings that should have been go-arounds and the number of accidents we have on landing is perhaps some indication that we don’t manage approach and landing as well as we should.
One of the reasons, I’d argue, for the lack of go-arounds is that you don’t see many go-arounds when you visit the large commercial airports. We aspire to the skills and professionalism of these pilots and so we assume that we shouldn’t be doing go-around either. The secret to the airline pilots consistency are stable approaches and each airline mandates what a stable approach should look like and at what point in the approach the plane must be stable. The commercial airline landing accidents are often traced back, through the flight recorder, to an approach that was unstable.
We should adopt this concept of stable approaches. We should define a point in space at which carious parameters of the approach should be met and we should promise ourselves that if we haven’t met these parameters by this point we’ll initiate the go-around right there and won’t attempt to “save” the landing.
Here are my ideas and suggestions for the parameters we might want to adopt when flying basic general aviation aircraft (Cessna 172, Mooney etc.).
VFR
When conditions are VFR we want some flexibility on how we manage the approach. At controlled airports we may need to accommodate the needs of the different speeds of traffic and make our approaches by entering a base leg, sometimes close in, sometimes further out. At uncontrolled airports we’ll fly a pattern that will have us line-up on final approach about 500ft AGL, but even here we may need some flexibility to shorten our approach or to lengthen our downwind to accomodate other traffic in the pattern.
For VFR approaches the point in space at which we will insist on a stable approach is 300ft AGL.
The parameters of a stable approach include:
- Aircraft configured, landing flaps set, gear down etc.
- Final approach airspeed stable and aircraft trimmed.
- Aircraft on the extended runway center-line.
- Aircraft on the normal glide-slope.
- Small changes in heading, pitch and power required to maintain the runway center-line and glide-slope.
- Sink rate no more than 700fpm.
The appropriate glide-slope (and sink-rate) is a matter for some discussion. For some pilots this will mean the visual glide-slope of a VASI or PAPI. For other pilots who like to conduct the entire approach from downwind at idle power it may mean a steeper glide-slope. So it’s YOUR normal glide-slope, you know if you’re too high or too low. One way to help you judge is do you have your “normal” power setting or are you make significant power changes to re-capture your normal glide-slope angle?
If you reach 300ft AGL and your approach is not stable as we’ve defined it here, then go-around. At best you’re going to “save” a poor landing, at worse you’re about to have a landing incident.
IFR (IMC)
This is a little harder for smaller general aviation aircraft because, in general, the landing configuration is not an appropriate configuration to use to fly the actual approach. Larger commercial aircraft can configure for landing and the approach and insist on a stable approach from a higher altitude, for example 1000ft.
I’d like to suggest that we trade-off runway length against ceiling, although unfortunately this trade-off doesn’t work to our advantage.
If the ceiling for the approach is at least 400 ft AGL then we can use our VFR stable approach definition. This will give us 100 ft to re-configure for landing before we must commit to land or go-around.
If the ceiling is lower then our trade-off is to require a longer runway which gives us a margin to accomplish the aircraft re-configuration and make a normal landing with runway to spare.