iFly Blog

 

In A Look at the Descent Leg, we discussed some of the steps pilots take upon vacating cruise altitude. With this post, we’ll go into more detail about the final portion of the descent segment: the approach and landing. As you probably know, this final segment is one of the most vital of the entire flight and requires the crew’s full attention. Let’s examine some of these duties your crewmembers perform.

Approach Speeds

The airspeeds used by airliners vary depending on temperature and aircraft weight. Prior to commencing the approach, pilots will calculate three (sometimes more) relevant speeds. The first, referred to as approach speed, is the speed flown during the latter stages of the final approach to just short of the runway threshold. This relatively slow speed permits a stabilized approach with the aircraft fully configured (landing gear and flaps extended). At times, approach speed will be adjusted for strong, gusty winds or when other than normal flap settings are used.

The second common speed, VYSE, provides the best climb rate with an engine inoperative. While engine failure during approach is extremely rare, flight crews always prepare for the worst-case scenario. Should a powerplant failure require an aborted landing, the crew is prepared with the requisite climbout speed.

VREF, the lowest of the three speeds, is the target airspeed when crossing the runway threshold. Once the aircraft is fully configured and the landing is assured, pilots will reduce power to achieve VREF. This speed is desirable because it reduces landing distance and stress on the landing gear & tires, and yet still maintains a safe margin above stalling speed. All three speeds are calculated and marked with speed bugs, which facilitate easy identification by the crew.

Configuring the Airplane

An important prerequisite for landing is to ensure the landing gear is extended and locked into position. How do the pilots know when to do this? Gear extension, flap deployment, and all other necessary tasks are specifically outlined in the landing approach profile. Your pilots will ALWAYS refer to checklists to verify these steps are completed correctly, but it’s a good bet most pilots also have these procedures memorized.

The landing gear and flaps also have their own V speeds, which indicate the maximum velocity they may be operated and/or remain in the extended position. During approach, pilots will slow the aircraft below these V speeds and deploy landing gear and flaps incrementally. You’ve probably seen the flaps extend during the approach, as well as heard a “clunk” as the landing gear locked into place. Rest assured, these extensions are far from arbitrary and are specifically spelled out for all conceivable types of approaches.

What happens if the gear fails to extend? While this possibility is rare, the aircraft manufacturers have built in numerous safeguards and backup extension plans. Your pilots have also trained ad nauseam to handle such problems. If, worst-case scenario, the gear still fails to extend, a safe landing is still probable. Usually, the crew will inform airport personnel to “foam the runway,” which reduces friction/sparks and the chance of fire. In addition, it’s a sure bet they’ll have fire trucks and ambulances standing by. When a belly landing is necessary, such an event is almost never fatal and any injuries received are usually minor.

Descent Angle

Airplanes normally descend at a 3 degree angle and receive guidance from both electronic and visual aids. At most commercial airports, airliners will fly an ILS (instrument landing system) approach, which gives lateral and vertical guidance. Though designed for instrument weather, nearly all crews still utilize this approach system in visual conditions. In many cases, they’ll let the autopilot fly most (sometimes all) of the approach. Next to the runways, external light systems also provide information on the aircraft’s approach angle to aid crews if adjustments are necessary. The combination of these systems can guide aircraft virtually to the pavement.

While the approach segment can be a nervous time for some passengers, the pilots have been thoroughly trained in every possible aspect of this phase. If something unexpected does occur, your crew is adequately prepared to handle the event. On your future flights, rest easy knowing you’re in the safe hands of an experienced crew.

 

When the tires squeak (or slam) onto the runway, many air travelers think the flight has ended. For pilots, an integral stage of the process still remains; one prone to confusion and with a notable risk for error. In From the Gate to the Runway, we discussed the confusion and hazards of taxiing at large airports, as well as the tools pilots have to assist them with the taxi process. In this post, we’ll cover taxi on the other end of the flight, once the plane has landed and is ready to unload.

Clearing the Active

After touching down and sufficiently slowing the airplane, the crew’s next objective is to exit the runway. Per air traffic regulations, only one aircraft (with limited exceptions) can be on an active runway at a time. However long a just-landed airplane remains on the runway, no other planes can use that runway to takeoff or land. At commercial airports, with hundreds of operations per hour, every second of delay can potentially clog an already congested aerodrome. Therefore, pilots look to minimize the time they remain on the runway after landing (without sacrificing safety).

To aid aircraft egress from the strip, major airports usually have high-speed taxiways next to the runways. These wide taxiways are constructed so they turn off at a gradual angle, thus permitting planes to exit the runway at a fairly high speed. High-speed turnoffs are so effective that controllers often instruct landing planes to “continue to the high-speed,” even though another turnoff may be nearer.

If no high-speed taxiway exists, pilots are (unless otherwise instructed) expected to turn off at the nearest taxiway (ahead of the airplane) once the aircraft is adequately slowed. While exiting the runway in a timely manner is favorable, pilots will delay if necessary in the interest of safety.

The Maze and the Aids

Upon exiting (“clearing” in aviation jargon) the runway, pilots contact ground control for taxi instructions. At this point, taxiing is essentially identical to the process discussed in From the Gate to the Runway, albeit in reverse order. The airport layout is oftentimes confusing, and pilots will utilize taxi diagrams, lights, signs, pavement markings, and ground control for assistance. As always, certain risks are inherent to the taxi phase, and your crewmembers follow established procedures to minimize these risks to the extent possible.

At the Ramp

Upon reaching the terminal ramp, most airliners are given one of two instructions: taxi to the gate or hold for a gate. When no gate is available, the plane will be directed to a ground holding area, commonly referred to as the “penalty box,” until a gate becomes available. Once a gate is ready, the crew will taxi to the directed gate to begin the parking process.

Parking the Bird

Parking an airliner requires a high degree of attention and planning. During this phase, ground tugs, conveyor belts, fuel trucks, baggage trams, food trucks (if you’re lucky), airstairs, and ground personnel might all be moving around near the jetway. Your pilots must ensure they don’t hit any of these moving targets while also controlling a multistory, megaton vehicle. In addition, airliners have lengthy wings protruding from both sides, another challenge to consider.

To aid with obstacle clearance, ground crews include wing walkers. Wing walkers don’t actually stroll along the airfoil, but rather advise (from the tarmac) the crew of the wings’ relation to nearby obstacles. For this, the wing walkers use hand signals, often with the aid of bright orange batons.

Once lined up with the parking tee, the crew proceeds slowly toward the signalman. Just imagine; a massive airliner can do some extensive damage if it accidentally taps the terminal, so pilots take every precaution to avoid such an outcome. Once signaled to stop, the Captain will set the brakes, shut down the engines, and review the parking checklist with the first officer.

Though a short flight segment, the final taxi phase consists of several essential factors. Your crew is well aware of each step’s importance, and thus doesn’t consider the flight over until they exit the aircraft. Next time you fly, think about your crew’s responsibilities during the taxi to the gate.