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April 1, 1999
Cowboys used lassos to "keep them doggies movin.'" Air traffic controllers use LAHSO to keep aircraft moving at busy airports. LAHSO is the abbreviation for land and hold short operations, and it has become a controversial procedure. There are significant safety implications for GA pilots, so you should understand LAHSO well in order to avoid the regulatory noose. LAHSO is used at most big airports that many of us don't fly to. But it can be used at many GA-only airports with control towers and intersecting runways. All pilots and instructors need to understand the pitfalls of this operation.
Thirty years ago, a program called simultaneous operations on intersecting runways was created in order to increase airport capacity. The idea was to land one aircraft and have it hold short of the intersection so that another arriving or departing aircraft could use the full length of the crossing runway. Increasing traffic brought the demand to expand the scope of the program and LAHSO was born in 1997.
Weather minimums required for LAHSO are a 1,500-foot ceiling and three miles' visibility. (If the runway is equipped with precision approach path indicators [PAPI], then weather can be as low as 1,000 feet and three miles.)
The program works, but there have been 20 incidents since 1994, according to the FAA, and the potential for mishap can be high at certain locations. Both air carrier and GA pilots have been guilty of transgressions. The Air Line Pilots Association and other pilot unions have never been very fond of it. There is good reason to be wary, because a blown LAHSO clearance may put two aircraft on a collision course and will certainly attract regulatory attention for failing to adhere to an ATC clearance. There have been events involving air carrier aircraft, GA aircraft, and a mix of the two. Let's look at some episodes from NASA's Aviation Safety Reporting System (ASRS).
"I received a clearance to land on Runway 8 and hold short of Runway 15, a normal practice at this airport. I acknowledged the clearance. On final approach the aircraft was high and in losing altitude we arrived at the threshold fast." The pilot believed that he could stop before the intersection, but because of the high airspeed the Piper PA-32 landed long and then ballooned during the attempted touchdown. The Piper did stop with maximum braking before actually entering the intersection, but it crossed the hold-short line.
A Beech Baron that was cleared to land without restriction arrived at the intersection simultaneously and stopped with heavy braking. The Piper pilot stated, "In retrospect, I wish I had initiated a go-around while on short final. Earlier acknowledgement of the problem would have resulted in less 'pucker factor' for all concerned."
This typical situation highlights some essential areas that pilots should be aware of when accepting LAHSO clearances. The pilot is required to read back the restriction and has the authority to decline any LAHSO clearance, regardless of circumstance. The monkey is clearly on your back if you accept. The available landing distance is listed in the Airport/Facility Directory for preflight planning at all airports that have LAHSO operations. If you don't have that good book available, just ask the controller what the distance is to the intersection. Know the landing distance for projected weight and weather, know the available landing distance, and plan to use every foot of the runway judiciously. Remember that glideslope and visual landing aids generally lead to a touchdown about 1,000 feet down the runway, which could lead to an intersection overshoot. We suggest going below glideslope on short final when obstacles are cleared so that the unused portion of the runway is kept to a minimum. There are other considerations that merit your caution and we'll discuss them later in this article.
When was the last time you did a short-field landing? In one of the FAA's pamphlets describing LAHSO, there is a cryptic note indicating that many LAHSO runway combinations provide generous margins but others may provide very little. Guess who makes the decision as to whether it's safe? Not the controller who clears you for the approach. Safe landing distances are based on multiple factors: the aircraft's landing weight, flap setting, and final approach speed. The airport elevation, temperature, and wind component all need to be taken into account along with the runway slope. Is the runway dry or wet? The distances are based on the aircraft's being no higher than 50 feet agl when crossing the threshold and on speed. If you're high or fast, as in the example, life could become very complicated in a few seconds. An early go-around is recommended if there is any doubt.
The FAA contends that LAHSO operations can be conducted safely on some runways after dark, but there are restrictions. We suggest that you increase the margins significantly. Double or even triple the book numbers for landing over a 50-foot obstacle. It's conservative — but remember that your certificate is on the line.
Night operations add complexity because the intersection that you are required to hold short of may not be clearly identifiable. Hold-short position lights must be installed on the restricted runway but the FAA is allowing a grace period on this. Without a VASI, PAPI, or ILS, the aim point may be difficult to visualize. Night LAHSO requires visual vertical guidance to be installed within one year. Until then, electronic guidance will be acceptable. These landing aids typically lead to a touchdown 1,000 feet from the threshold. With only 3,500 feet of available landing distance to the intersection, for example, the guidance systems could result in a relatively long landing and a busted LAHSO clearance.
Wet pavement adds more spice to an already dicey mixture. For the time being, LAHSO will only be conducted under dry conditions until there is a better understanding regarding landing distances for wet landings. The FAA recommends that under wet conditions, you check the tire pressure, since underinflated tires can contribute to dynamic hydroplaning. This strikes me as pushing the envelope. If the available runway is so short that the tires have to be perfectly inflated, this clearance should be declined.
One of the biggest concerns that airline pilots have is the reduced option for a go-around or a balked landing. Pilots should always have this most basic escape tool as an option. While the FAA says that LAHSO does not preclude a rejected landing, you are tasked with maintaining safe separation from other aircraft and vehicles. If the tower believes that separation was compromised, expect an invitation to chat. Advise ATC as soon as possible if you decide to go around. This will give controllers extra time to help you take evasive action.
"I was shooting an ILS in visual conditions on Runway 8. A commuter plane was holding in position on Runway 15. The tower thought the approach was going fine and released the commuter for takeoff. I was cleared to land and told to hold short of 15. After noticing that I couldn't comply with the LAHSO clearance, I opted for a go-around. While climbing out the commuter rotated for takeoff and if I continued, my aircraft would be in his flight path. I advised the tower that I was making a right turn to avoid traffic but the tower cleared me to continue straight out. I returned to the pattern, was cleared to land on Runway 15, and [was] told to call the tower ASAP due to a possible deviation."
This ASRS report shows that in certain circumstances, even a conservative decision may lead to a hassle with Flight Standards. The FAA's pamphlet on LAHSO operations is chock-full of reasons why this may be a bad deal. Here are some more cautions: Decline a LAHSO whenever there is potential for a wake-vortex encounter, especially if you are flying high above and behind the wake-generating aircraft. This could lead to a potentially long landing or a wake encounter if you try to drop down to the threshold to avoid the overshoot. Be cautious of displaced thresholds. Avoid a LAHSO if tailwinds are above 10 kt within 1,000 feet of the surface. Crosswinds above 15 kt or above the aircraft's demonstrated crosswind component, whichever is lower, also suggest a declined clearance. Nearby thunderstorms or wind shear may cause a flight to use extra runway, so LAHSO is not recommended. LAHSO operations will be suspended for 20 minutes if wind shear is reported.
If you decline a LAHSO there may be a delay in your arrival, but that's trivial compared to the inconvenience of a collision or a certificate action. I've flown at a number of air carrier airports where LAHSO is routinely used to keep GA and airline traffic moving. At Philadelphia International and Lambert-St. Louis International it is a way of life, and the landing distances have always been more than adequate for my light aircraft; but I've also limited the approaches to day-VFR, dry conditions. Under other circumstances I've advised the controller "unable" and then made a speed adjustment or received a delaying vector. These are small concessions — and it sure beats having the LAHSO noose around your neck.
See also the index of "Safety Pilot" articles, organized by subject. Visit the ASF Web site ( www.aopa.org/asf/publications/lahso.html) for more information on LAHSO. Bruce Landsberg is executive director of the AOPA Air Safety Foundation.
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