Missed Approach

The news reports lauded the pilot for his flying skill, and that's fine. But I had to wonder what he was thinking about as he pressed on into that approach. If it looked bad on video, it must have really looked bad from the cockpit. The pilot did finally become a wise man when he elected to abort the landing.

In aviation we have always embraced variable terminology. Some would call this a go-around, some would call it a missed approach, and others might call it an aborted or rejected landing. Generally a go-around is thought of as a VFR maneuver and a missed approach an IFR maneuver. I guess a rejected landing would be one abandoned at the last minute and an abort would come after the wheels have touched down. Whatever, the decision-making becomes critical when things are not going well during the approach and landing phase of flight.

There have recently been a number of accidents, serious and otherwise, where a missed approach would have taken, and perhaps kept, the airplane out of harm's way. Certainly when we look at accidents during this phase of flight it is possible to identify a point where it was obvious that things were going bad.

Stabilized approaches, with everything configured for landing, with the airplane smoothly tracking the localizer and glideslope, and with the speed on Vref, are holy in turbine airplane operations. It is generally held that the approach should be stabilized at 1,000 feet if in instrument conditions and at 500 feet if in visual conditions. This is fine and necessary in heavier airplanes, and there is a long history of unstabilized approaches leading to accidents. Over a third of airline accidents occur when the crew fails to abort an unstabilized approach. Certainly any approach that involves substantial changes in power, attitude or heading below those guideline altitudes is a bad one.

Using those guidelines it is possible to make an early decision on a missed approach. If things are not stabilized at that specified point on an approach, miss it and try again. Pilots, though, often tend to press on and try to patch things up. That's bad because the later you wait to start a missed approach, the more lethal the outcome can be. This can be as true in light airplanes as in heavier ones, but light airplanes are more often operated on runways that are substantially longer than necessary. Still, light airplanes are damaged or destroyed during landings that follow approaches that should have been missed.

Two accidents on the same runway, 24, at Carlsbad, California, bear an eerie similarity right up until the last, where the outcome delivers a strong message on this subject. Information is from the NTSB reports on the accidents.

Both airplanes were Citations, one a 560 and one a 510 (Mustang). The 560 had a crew of two, the 510 was single pilot. There were pilot factors in both cases. The captain of the 560 had type 2 diabetes (not reported to the FAA) and post-accident toxicology testing was consistent with an elevated average blood sugar level over the previous several months. On this flight, the 510 pilot had experienced avionics problems and an autopilot outage, and noted "that he was overwhelmed with the electrical failures and fatigued from maneuvering the airplane by hand for such a long duration (which he approximated was about 45 minutes)."

In both cases the pilot approached the 4,897-foot-long runway high and fast and there was a tailwind component for the 560 landing.

Both airplanes landed approximately halfway down the runway. The 510 pilot determined that he wasn't going to be able to stop within the confines of the runway and that he wouldn't be able to abort the landing because of diminished speed, so he elected to try a groundloop. The airplane came to rest south of the runway with the main gear collapsed, the flaps folded under the wings, and with the four people on board uninjured.

The 560 crew faced much the same situation and the captain delayed the initiation of a go-around until the first officer asked if they were going around. The aircraft lifted off before departing the paved overrun. It hit a localizer antenna platform 304 feet off the end of the runway and 2 feet lower than the elevation of the end of the runway. It went 400 feet farther, over downsloping terrain before colliding with terrain and a commercial storage building that was approximately 80 feet lower than the end of the runway. The four people in that one perished.

The moral to the story is clear. If you press on into a landing out of a lousy approach, a point is passed where a successful go-around is impossible. There is no way to know precisely where that point is but the record suggests that once the wheels of the airplane are on the ground, they are best left there. Certainly an accident that occurs when you are slowing down can have a better outcome than one where you are speeding up.

There is another critical point on an approach where a last-minute grade on the approach needs to be made. On a precision approach, where the glideslope will take you to a touchdown point about 1,000 feet down the runway, the threshold crossing height (TCH) is usually 50 feet. Why is that critical? Well, it's where an important characteristic of the airplane starts to change. Once the airplane is in ground effect, which is in full effect at an altitude half the span of the airplane, the airplane decelerates more slowly, about half as rapidly, than it decelerates out of ground effect. This characteristic is especially marked on airplanes that sit low to the ground, as do the 500 series Citations and Mooneys to name a couple.

So, if the speed at the TCH is a little high, best get rid of the extra knots before the airplane settles into ground effect. If the speed is a lot higher, then the approach should be missed unless the runway is many times longer than the value shown in the book for the airplane.

The effect of extra speed on landing distance can be pronounced, especially if that extra speed is maintained into ground effect and the landing flare. You can take available numbers and calculate a 10 percent increase in the landing roll for each 2.5 knots speed over the POH touchdown speed. You can also postulate a 20 percent increase in landing distance for each 2.5 knots over Vref at 50 feet on approach if the extra speed is carried into ground effect. Most of our book landing distance numbers are low but can become long when you start adding substantial percentages for knots of extra speed.

Another reason to miss an approach that is flown too fast is that it makes the landing that follows awkward at best and damaging at worst. Tricycle-gear airplanes are designed to be landed on the main wheels first. If the nosewheel hits first, either because the pilot "plants" the airplane on the runway at high speed or bounces and enters a pilot-induced porpoise, then the nose of the airplane is in great jeopardy. Bent firewalls, collapsed nosewheels and damaged propellers are common occurrences. Life is much better if a go-around is initiated early on, or at the latest, at the threshold crossing height if everything is not just right.

In tailwheel airplanes it's possible to land at higher speeds safely by making wheel landings or by flying the airplane onto the runway on the main wheels first. There the technique is actually to add a little forward pressure on the stick or wheel at the moment of touchdown. That does not work in tricycles.

In a tricycle-gear airplane the only way to safely touch at a higher speed is to use less than full flaps. So if a crosswind or turbulence dictates a little extra speed, consider landing with less than full flaps. Make sure there is adequate runway, remembering that, for example, 10 degrees less flaps might mean a 5 knot higher touchdown speed. That in turn might increase the landing roll by 20 percent. If this doesn't calculate, miss the approach and go to a longer runway more nearly aligned with the wind.

When clouds are added to the picture the missed approach is related both to landing considerations and to weather.

For best results it is best to fly every instrument approach with full anticipation of a missed approach. There are many things that can lead to a miss. If the approach is being hand flown and at 1,000 feet above the ground everything is not well in hand, that's a good place to start into the missed approach. Just remember that the missed approach procedure begins at the missed approach point, usually the end of the runway on non-precision approaches, so you don't start the published procedure until reaching that point.

Another thing to consider on a non-precision approach is that the point at which the approach becomes impossible is not at the missed approach point but a distance from the end of the runway. With GPS we have distance to the end of the runway and when that number equals the visibility minimum for the approach, successfully completing the approach is in doubt unless the runway is in sight.

This is illustrated in the minimums for some LNAV/VNAV and LPV approaches. On these, if the decision height is, say, 400 feet, the visibility minimum will be higher than the usual one mile for a straight-in LNAV approach. Why? If you are following the calculated (usually 3-degrees) approach slope to the runway you'll be more than a mile from the end of the runway when reaching the decision height. There are many non-precision approaches where the minimum descent height makes it impossible to make a straight-in approach if the visibility is minimum, and the criteria for minimums on the GPS approaches with vertical guidance addresses this.

Another reason to always anticipate a missed approach is weather. It might be reported as above minimums at the airport, but that offers no guarantee of what the weather will be along the final approach course. Under Part 91, not for hire, we can fly approaches when the visibility is reported as below the published minimums because our rule says the flight visibility has to meet the criteria, and flight visibility is based on what you see ahead and not what is observed on the ground.

What's legal isn't always safe and there is a long history of fatal accidents related to approaches in low weather. This is especially true when multiple approaches are flown by a pilot who is really trying too hard to make possible the impossible.

There are also accidents on missed approaches, either when the pilot doesn't aggressively fly into the missed approach procedure or loses control of the airplane because of the distractions found in a missed approach. On the latter, if every approach is begun with a firm plan for what comes next in the event of a missed approach, things will be better. Have an answer in mind for the controller's question about your intentions after you miss an approach and the rest of your day will go better.

Next, consider the flying technique involved in a missed approach. One thing we can do to make missed approaches easier is to fly the approach with takeoff flaps and at the initial climb airspeed. That means you have to calculate extra runway but most ILS runways will allow this in piston singles or light twins. If an approach flown like that is missed, the airplane will be in the climb configuration from the git-go on the missed approach, leaving only the application of power and the gear to be retracted if the airplane is so equipped.

A shorter runway served by a non-precision approach probably won't allow such an approach, but the minimums would likely allow the selection of full flaps after the runway is in sight and the landing is assured. When you are practicing do look at missed approaches frequently.

Finally, a good practice is to eschew approaches that have a high likelihood of becoming missed approaches. If the weather is really low, do you want to fly within 200 feet of the ground while fully enveloped in cloud? There is a lot of difference between a professional flight crew's qualifications to do that and the average instrument rated pilot's qualifications to do that. Our training falls far short and doing it alone has fewer safeguards and backups. That's why our record here is so bad, and their record is so good.

Choosing your approach battles carefully can reduce a lot of the known risks. If your destination has weather or wind or runway length problems there is surely another airport available with better conditions.