getting stopped painlessly, in time
March 25, 2019
Taxiing an aircraft safely presents many unique challenges to a pilot. Capt. LeRoy Cook lists these challenges and offer advice to bring an airplane down to a walk
Bringing an aircraft safely to taxi and turnoff speed after making an approach to the runway is a necessary exercise, one important enough that we must take extensive pains to make sure we’re not involved in a “runway overshoot” or “runway end excursion”. Leaving the runway surface is almost guaranteed to cause expensive damage to the aircraft, and our career, insurance coverage notwithstanding. We should assure that the airplane can be safely landed on a chosen runway, and that we’re up to the task on a given day.
Begin the process of safely landing the aircraft by properly planning; know how much runway you need, factoring in weight, temperature and wind conditions, runway surface and obstructions. Landing distances from the FMS or ops manual charts are a basis, but they should be regarded as minimums, not as absolute sufficiency. If you have any doubt, there is no doubt – go to a longer runway.
Once it is determined that the destination runway is adequate, make sure you are flying a profile that will place the airplane’s wheels on the surface within a normal touchdown zone, with speed managed so as to begin the rollout with an acceptable amount of energy to be dissipated. This task begins with a stabilized approach, despite ATC’s traffic separation requirements, meaning you don’t want to be trying to slow down at the last second, flying at Vref plus 20 knots while the VASI lights are stubbornly white in the lower part of your windshield. Get the airplane on target by three miles out and 500 feet AGL, or start planning a go-around.
Runway overshoot accidents generally result from a hasty unstabilized approach or a contaminated runway that wasn’t considered when the flight was planned. We can’t always expect a dry, level runway, free of snow and ice, but it shouldn’t come as a surprise when we find a slick surface; check ASOS or ATIS for reports of precipitation, seek runway condition reports from ATC and watch out for pilot reports that are being altered to “good” or “mostly dry” to cover an operator’s requirements.
When asked to provide a runway condition report, go beyond a one-word response; if areas of standing water or patchy snow are present, report their location as “touchdown zone” or “rollout” or “departure end” if appropriate. Other pilots need to know if the runway isn’t clean overall. Braking action reports are fairly subjective, depending on aircraft type and pilot observation, but be honest about what you found.
Stabilizing the approach becomes even more important when the runway is contaminated. Fly the speed appropriate for your aircraft’s configuration; if you’re light, you should expect to use a Vref slower than when at max landing weight, avoiding extra float in the flare. Similarly, your target spot on the runway must be in the sacred first 1,000 feet, or at least the first third. Combining approach speed and glideslope target should produce a good touchdown with adequate runway remaining. Remember, you always have the option of going around if the approach isn’t working out.
That said, going around becomes a riskier option as the landing progresses. It’s relatively easy to pull up out of the hole while still at Vref, a few hundred feet above the ground; it’s quite another to power-up and reconfigure after the tires are on the runway, already slowing down with flaps and spoilers deployed. In general, once the flare is begun and the airplane is no longer at approach speed, it’s best to consider the landing made.
Go around while rolling only if there’s a clear reason to do so, because an accident is likely if you don’t act immediately. Such a case might be an aircraft or vehicle entering your runway, wildlife hazard or unexpected wind shift.
Whoa, Big Fella
So, if you planned properly, flew the approach in a stable, slow manner and touched down in the correct zone, a normal rollout and exit should be assured. Braking technique is important, however; the landing isn’t over, said my old instructor, until the chocks are under the wheels. Deceleration takes more than standing on the pedals. Use everything appropriate to the aircraft’s recommended procedures.
When it comes to achieving the handbook stopping distances, it’s best to stick with the methods recommended by the aircraft manufacturer. Company testing found what works most consistently, using average, but aggressive, piloting technique. Use other methods only if you want to act as a test pilot. One of the first requirements is to immediately apply full brakes and hold the pressure, especially if anti-skid equipped. Pumping brakes or delaying application is simply adding unwanted stopping distance.
Should the runway be wet, hydroplaning is a definite hazard, but it can be managed by letting the ABS cycle or cycling brake pressure if you feel a lack of deceleration, caused by locked-up wheels. If you see a slick, shiny runway, make your touchdown firm, rather than trying for a soft, roll-on landing. That doesn’t mean pushing the airplane on the ground at excessive speed, which only encouraging hydroplaning, but rather allowing the tires to sink onto the wet surface with enough force to break through the layer of water.
You’re Down, Now What?
Some aircraft handbooks encourage raising the flaps after touchdown to increase the weight on the wheels, which improves brake effectiveness by removing lift. Most of our airplanes have enough weight to preclude this requirement, which carries the risk of inadvertent gear retraction. If you’re equipped with armed ground spoilers and lift-dump systems, verify they’ve functioned and slowing is normal.
Reverse thrust is a comforting adjunct to wheel brakes, but it must be used appropriately. If in a turboprop, select propeller condition to proper idle setting, move briskly into Beta and increase power as recommended, remembering to come out of reverse before decelerating to a speed that might generate FOD or prop erosion. Steer aggressively to guard against swerving or sliding.
Jets with reverse thrust are also much better equipped to handle a slick runway, but also have limitations to be observed. Excessive reverse on a contaminated surface can create unwanted yaw motion, most particularly with fuselage-mounted engines. Again, be prepared to use aggressive steering and come out of reverse at the first sign of loss of directional control.
Crosswind operation has an effect on stopping distances, in that the benefit of an all-headwind component is lost and braking is slightly compromised if good controls application is not maintained. In most cases, the effect is minor but pilots may be tempted to use extra speed for their approach because they think the crosswind requires added control. Do not pad Vref numbers excessively, just because the crosswind is present. More importantly, factor the tailwind or headwind effect into your base leg planning, which can cause you to wind up higher or lower than you might normally be when you roll out onto final.
As you progress down the runway, you should have plenty of stopping distance ahead, because you planned your touchdown for the first portion of the runway and you maintained an approach speed that was no more than appropriate to avoid a stall and provide control. Keep braking; it’s more efficient to use heavy braking right after touching down than to jam on brakes in a panic as the runway end approaches.
Air traffic controllers seem to be ever-more prone to issue commands to exit at specific taxiways or seek a response about parking while we are still in the early stages of a landing rollout. If you aren’t able to comply, respond with “Unable” right away and deal with control of the aircraft first. If you were issued a “Land and Hold Short” landing clearance, you are expected to carry it out because you accepted it as issued. The time to refuse LAHSO is when it’s first brought up, not after you’re on the rollout.
As the rollout continues, you may, in the absence of ATC instructions, spare the brakes and reverse thrust to roll out to the end. A longer taxi may better suit your brake and engine cooling concerns. However, we often try for that mid-field turnoff in order to reach a favorite FBO or terminal. Don’t abuse the aircraft and passengers with rough stopping technique, just to show off your prowess as a STOL pilot.
Bringing an airplane down to a walk is another example of proper energy management, begun early in the process so there are no surprises as the runway distance-to-go markers flash past. Done correctly, there should never be a reason for the tower controller to quip “speed permitting, exit at the end.”