Over the course of many airport projects that I’ve worked on, one question that has returned in various forms is “What is the necessary wingtip separation distance for aircraft parked at a gate”.

For airports outside the United States, the answer is fairly straightforward. The International Civil Aviation Organization (ICAO) which issues worldwide regulatory standards that are applied by national Civil Aviation Authorities including the FAA in the United States stipulates in Annex 14:

3.13.6 Recommendation: An Aircraft stand should provide the following minimum clearance between an aircraft entering or exiting the strand and any adjacent building, aircraft on another stand and other objects.

Table 1 shows the different ICAO wingtip separation standards.

Table 2 converts ICAO standards to the FAA ADG classification and the Imperial system.

While most countries apply the ICAO standards directly into their own standards, the FAA does not provide specific guidance in Advisory Circular (AC) 150/5300-13A Change 1. The closest the AC addresses the issue is in the section “Apron Design”.

 The primary design consideration is to provide adequate wingtip clearances for the aircraft positions and the associated taxilanes. 

Clearances. Apron design must at all times allow aircraft to maintain appropriate wingtip clearance during apron movement activities.

While the FAA does not provide guidance on wingtip separation, the Airport Cooperative Research Program (ACRP) working under the Transportation Research Board (TRB) adopts the ICAO standards in the Airport Passenger Terminal Planning and Design Guidebook Volume 1. However, further in the guidebook it is stated that certain airports or airlines may require 25 feet separation between wingtips. 

In the US, airlines have often developed their own gating standards largely based on ICAO standards and their insurance covenants. Generally, these standards require at least 25 feet between wingtips, though there are often provisions to allow for 15 feet wingtip separation if the two neighboring aircraft are from the same airline and ADG-III. Any aircraft neighboring an ADG-IV or larger aircraft should have at least 25 feet wingtip separation even if one of the aircraft is an ADG-III aircraft. One particularity is that some airlines may require more than 25 feet between a parallel (to the fuselage) service road and the wingtip to improve ground handling operations and ramp safety. 

Though IATA recommends head of stand service roads in the IATA ADRM, tail of stand service roads are used at most airports in the United States. The result is that service vehicles needing to access the front of the aircraft usually have to thread through wingtips of neighboring aircraft. The wider the distance, the smaller the risk of a vehicle striking an aircraft and also vehicles movements become more efficient. If an airport uses fueling trucks instead of hydrant fueling for example, a 15 foot wingtip separation would block off access to the front of the aircraft if refueling is in progress.

Wingtip clearance must also be maintained during aircraft power-in and pushback. Often planners will place an aircraft in plan view ensuring that there is sufficient wingtip clearance when the aircraft are parked but do not account for clearance when the aircraft is in movement. Often, the necessary wingtip clearance falls below requirements when the parking position is in a corner and the wingtip could strike a neighboring aircraft’s horizontal stabilizer on power-in or pushback. Tools such as Transoft AviPlan can help model the movement in great detail, however a properly drawn CAD block of an aircraft with offsets showing safety lines can help determine if requirements are met if a movement simulation software is not available. 

Generally for high-level and preliminary planning, 25 feet is the standard de rigeur. If gate allocation and the operating airline is known during planning, obtaining the airline gate planning specifications would remove a lot of the guesswork if apron area is at a premium. Working with airport operations and the airlines to obtain consensus on planning specifications will ensure a smoother design process with fewer questions left to answer further in planning or design. 

Ground Service Equipment placement and movements

Every commercial aircraft manufacturer publishes an airport planning manual which contains operating characteristics and planning requirements for their aircraft. These resources are usually freely  available on their websites. One section contained in these manuals is ground service equipment layout. While these layouts provide crucial information, how they are applied in the real world vary greatly from airline to airline and sometimes from airport to airport. How ground servicing equipment is arranged and timed can greatly affect the space requirements for a gate. While high-level gate planning usually will only look at aircraft placement, a more detailed analysis will be required to validate any parking layout. Ideally this should occur either in advanced planning or during a Program Definition Document (or similar). 

A static configuration as shown by the aircraft manufacturer planning manuals only shows a partial picture. In reality, vehicles around an aircraft come and go depending on their function, their timing is subject to in-depth studies and constant operational improvements to reduce the amount of time an aircraft needs to be on the ground. How the vehicles get into service position and move about the apron without impacting other ground handling operations while maintaining a safe distance from all aircraft is often overlooked during planning and even well into design. Some vehicles have limitations on how tight they can turn or on rearward visibility which makes backing up potentially hazardous. 

While not always necessary, an aircraft turnaround simulation that can simulate in real time (or accelerated) an aircraft turn. From the moment the aircraft powers-in to the gate and until the moment it pushes back and is detached from the pushback tug; all GSE movements that service the aircraft are simulated and potential conflicts and issues can be dealt with before it becomes a change order.

The best source of information to populate the simulation is observing multiple aircraft turns, noting which vehicles are used, when they arrive, when they leave and how they operate. The higher the amount of turns, the more accurate the simulation will be. 

The gating analysis should take into account the vehicle type/model, number, configuration and timing of the following (some may not be used):

• Aircraft tow truck
• Catering trucks
  • Front and rear configuration
• Fueling
  • Hydrant (truck or cart) or Fuel Truck
• Baggage
  • Front and rear configuration
  • Bags loaded by container or individually
  • Bag Train configuration, number of carts
• Cargo
  • Use of Cargo loader
  • Cargo Train configuration, number of carts
• Lavatory Vehicle
• Potable Water Truck
• Cleaning Staff transport
• Airstairs
• Ground Power Unit (if not provided by the PBB or an in-ground system)
• Air Conditioning Unit (if not provided by the PBB)

Some additional information that would enhance accuracy:

• Wingtip separation as required by airport/airline (if unavailable use 25 feet)
• Passenger Boarding Bridge Type and length (if available)

Some examples of issues include:

The newest generations of 737 aircraft, the MAXes and the last -700/800/900 equipped with split scimitar winglets can present an additional obstacle to ground handlers. The wings of a 737 are lower to the ground than its counterpart the A320. While some bag tugs can move under the wing of an A320, this is not possible with a 737. 

While you may not need to complete a full simulation for every aircraft at a gate, the representative critical aircraft may suffice (usually the largest aircraft for a certain Code/ADG). However due to differences in aircraft layout some vehicles would have trouble accessing its service position on one type of aircraft but not on others. For example, if two aircraft are parked at intersecting angles, the wings of one aircraft may block access to the R1 door on usually used by catering on the neighboring aircraft. If a static image is used during planning, there is enough space for the truck. Often overlooked, is that there is no way for the truck to drive into position without hitting the wing of another aircraft. 

When planning an aircraft gate, different issues can arise that may require some configurations to be completely revised or certain requirements relaxed. Knowing lessons learned from previous projects can move your project forward.