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Taxiing

Introduction:

  • Taxiing refers to the movement of an aircraft while on the ground, under its own power
  • Since taxiing involves coordination, ground control will issue clearances to operate
  • Once your engine has started you must be aware of what you're doing and keep a visual scan, your "flight" has begun
    • It may be required initially to tow the aircraft before engines are started to be safe

Clearance Requirements:

  • Clearances are required prior to moving an aircraft or vehicle onto the movement area during the hours an Air Traffic Control Tower (ATCT) is in operation
  • The movement area is normally described in local bulletins issued by the airport manager
    • These bulletins may be found in FSSs, fixed base operators offices, air carrier offices, and operations offices
  • A clearance must be obtained prior to taxiing on a runway, taking off, or landing during the hours an Airport Traffic Control Tower is in operation
  • When assigned a takeoff runway, ATC will first specify the runway, issue taxi instructions, and state any hold short instructions or runway crossing clearances if the taxi route will cross a runway. This does not authorize the aircraft to "enter" or "cross" the assigned departure runway at any point. In order to preclude misunderstandings in radio communications, ATC will not use the word "cleared" in conjunction with authorization for aircraft to taxi
  • ATC will issue an explicit clearance for all runway crossings
  • If a pilot is expected to hold short of a runway approach ("APPCH") area or ILS holding position (see FIG 2−3−15, Taxiways Located in Runway Approach Area), ATC will issue instructions
  • Taxi For Takeoff:

    1. Complete all checklists required before taxi
    2. Listen to ATIS/AWOS/ASOS, as appropriate
    3. Contact Clearance Delivery, as appropriate
    4. Contact Ground Control:
      • State with your aircraft identification, location, type of operation planned (VFR or IFR), the point of first intended landing, and that you have the appropriate ATIS/AWOS/ASOS code:
        • Pilot: "[Agency] Ground, [Callsign], [Location], [Operation] with [Information]"
        • Pilot" "Washington ground, Beechcraft One Three One Five Niner at hangar eight, ready to taxi, I−F−R to Chicago, with information Alpha"
    5. Ground will respond with your instructions:
      • ATC will first specify the runway, issue taxi instructions, and then state any required hold short instructions
      • "Taxi to" means you are cleared to cross all taxiways and runways excepting the assigned takeoff runway
      • "Hold short" means you cannot cross said runway or taxiway until cleared
      • ATC is required to issue "hold shorts" or "cleared to cross" on any runway active or not in between you and your destination
        • Ground: "Beechcraft one three one five niner, Washington ground, runway two seven, taxi via taxiways Charlie and Delta, hold short of runway three three left"
    6. Acknowledge the taxi clearance:
      • When taxi instructions are received from the controller, pilots should always read back:
        • Runway assignment
        • Any clearance to enter a specific runway
        • Any instruction to hold short of a specific runway or line up and wait

        • Controllers are required to request a read-back of runway hold short assignment when it is not received from the pilot/vehicle
      • Aircraft: "Beechcraft One Three One Five Niner, hold short of runway three three left"
      • The control tower also issues bulletins describing areas where they cannot provide service due to non-visibility or other reasons
        • This is usually done through ATIS/AWOS remarks
    7. Check the heading indicator to ensure the reading has not precessed more than 3° in 15 minutes
  • Taxiing after Landing:

    • Exit without delay at the first available taxiway or as instructed
    • All parts of the aircraft must be across the hold short line to be considered off the runway
    • Contact ground when directed by tower
      • Aircraft: “Orlando ground, Beechcraft One Four Two Six One clearing runway one eight left at taxiway bravo three, request clearance to Page”
      • Tower: “Beechcraft One Four Two Six One, Orlando ground, hold short of runway one eight right”
      • Aircraft: “Beechcraft One Four Two Six One, hold short of runway one eight right”
  • Taxiing for Reasons Other Than Takeoff or Landing:

    • When issuing taxi instructions to any point other than an assigned takeoff runway, ATC will specify the point to taxi to, issue taxi instructions, and state any hold short instructions or runway crossing clearances if the taxi route will cross a runway. NOTE: ATC is required to obtain a read-back from the pilot of all runway hold short instructions

Operating Practices:

  • Good operating practice dictates that pilots acknowledge all runway crossing, hold short, or takeoff clearances unless there is some misunderstanding, at which time the pilot should query the controller until the clearance is understood
    • NOTE: Air traffic controllers are required to obtain from the pilot a read-back of all runway hold short instructions
  • Pilots operating a single pilot aircraft should monitor only assigned ATC communications after being cleared onto the active runway for departure. Single pilot aircraft should not monitor other than ATC communications until flight from Class B, Class C, or Class D surface area is completed. This same procedure should be practiced from after receipt of the clearance for landing until the landing and taxi activities are complete. Proper effective scanning for other aircraft, surface vehicles, or other objects should be continuously exercised in all cases
  • If the pilot is unfamiliar with the airport or for any reason confusion exists as to the correct taxi routing, a request may be made for progressive taxi instructions which include step-by-step routing directions. Progressive instructions may also be issued if the controller deems it necessary due to traffic or field conditions (for example, construction or closed taxiways)
  • At those airports where the U.S. Government operates the control tower and ATC has authorized noncompliance with the requirement for two-way radio communications while operating within the Class B, Class C, or Class D surface area, or at those airports where the U.S. Government does not operate the control tower and radio communications cannot be established, pilots must obtain a clearance by visual light signal prior to taxiing on a runway and prior to takeoff and landing
  • Especially at unfamiliar airports, taxi with the use of an airport diagram in order to maintain situational awareness
  • Upon reaching an intersection, you should get in the habit of telling yourself (or say allowed if with others) that the area is cleared
    • ATC: "Cleared left, forward and right, going [Left/Forward/Right]"

Relaying a Clearance:

  • The following phraseologies and procedures are used in radiotelephone communications with aeronautical ground stations
    1. Receipt of ATC clearance:

      • ARTCC clearances are relayed to pilots by airport traffic controllers in the following manner
        • Tower: "Beechcraft One Three One Five Niner, cleared to the Chicago Midway Airport via Victor Eight, maintain eight thousand"
        • Aircraft: "Beechcraft One Three One Five Niner, cleared to the Chicago Midway Airport via Victor Eight, maintain eight thousand"
    2. NOTE: Normally, an ATC IFR clearance is relayed to a pilot by the ground controller. At busy locations, however, pilots may be instructed by the ground controller to "contact clearance delivery" on a frequency designated for this purpose. No surveillance or control over the movement of traffic is exercised by this position of operation

Taxi Operations During Low Visibility:

  • Pilots and aircraft operators should be constantly aware that during certain low visibility conditions the movement of aircraft and vehicles on airports may not be visible to the tower controller
    • This may prevent visual confirmation of an aircraft’s adherence to taxi instructions
  • If pilots become disoriented, it is vitally important to notify the controller immediately
    • Pilots should proceed with extreme caution when taxiing toward the sun
    • When vision difficulties are encountered pilots should immediately inform the controller
  • Advisory Circular 120−57, Low Visibility Operations Surface Movement Guidance and Control System, commonly known as LVOSMGCS (pronounced "LVO SMIGS") describes an adequate example of a low visibility taxi plan for any airport which has takeoff or landing operations in less than 1,200 feet runway visual range (RVR) visibility conditions. These plans, which affect aircrew and vehicle operators, may incorporate additional lighting, markings, and procedures to control airport surface traffic. They will be addressed at two levels; operations less than 1,200 feet RVR to 500 feet RVR and operations less than 500 feet RVR
    • Specific lighting systems and surface markings may be found in Paragraph 2−1−11, Taxiway Lights, and Paragraph 2−3−4, Taxiway Markings
  • When low visibility conditions exist, pilots should focus their entire attention on the safe operation of the aircraft while it is moving. Checklists and nonessential communication should be withheld until the aircraft is stopped and the brakes set

Regulation:

  • Taxi/landing lights shall be utilized to the maximum extent possible at night except to avoid blinding another pilot
    • The use of takeoffs-and-landings/taxi lights is an effective means of illuminating surface hazards during taxi movements at night and alerting all concerned of an aircraft's presence/position in flight
  • FAR 91.209 has specific guidance as to lighting requirements

Airplane Flying Handbook, Crosswind Taxiing Technique
Figure 1: Airplane Flying Handbook, Crosswind Taxiing Technique

Taxi Operations:

  • Taxi Speed:

    • Taxi speed is not specifically regulated; however, common sense must apply so as not to operate in a careless or reckless manner (FAR 91.13)
      • You should never taxi any faster than a man can walk in the line
      • While on a taxiway, you should not taxi faster than a man could jog
      • When entering a turn, be mindful of the stress you are placing on the gear as you turn and slow down
      • Care must be exercised when taxiing at night, in low visibility, or toward the sun to remain situational awareness as to where you are
        • This means half the speed and twice the caution
  • Compensating for Airport Slopes:

    • Runways are generally flat surfaces however small changes in elevation will impact the speed at which the aircraft moves
      • You will require more power uphill and less downhill
      • Every turn you make will impact the amount of power required to some degree
      • It is unlikely however, that you'll need to adjust than around 100 RPM to overcome to effects of slope
  • Compensating for Wind during Taxi:

    • Wind can effect an aircraft, even when moving at slower speeds on the ground during taxi
      • Every turn you make, you should change the control positions
    • Moderate to strong headwinds and/or a strong propeller slipstream makes the use of the elevator sometimes necessary to control pitch
    • Downwind taxiing will usually require less power and may require none, but do not ride the brakes
    • The upwind wing will tend to be lifted by the wind unless the aileron control is held in that direction
    • Weathervaning may occur as the wind effects a large portion of the aircrafts side [Figure 4]
      • This is more apparent in a tail wheel aircraft
    • Remember to dive away and climb into the wind
Airplane Flying Handbook, Downwind Taxi
Figure 2: Airplane Flying Handbook,
Downwind Taxi

Technique:

  • It will require a large amount of power to initially move the aircraft
    • As the aircraft starts to move, power must be retarded, possibly as far back as idle, to prevent continued acceleration
  • Steer with rudders, keeping your feet over, but not on, the breaks
  • Riding the brakes will reduce their lifespan and could render them less effective
    • Many high performance aircraft can produce enough thrust that riding the brakes may be necessary to keep the aircraft from speeding up; brake judiciously
  • Airplane Flying Handbook, Quartering Tailwind
    Figure 3: Airplane Flying Handbook,
    Quartering Tailwind
  • Jet aircraft can be dangerous when exhaust is swept across an area
  • Reduce the power to idle in a turn, but remember an aircraft stopped in a turn takes a lot of power to get moving again
    • Always execute good "tail pipe courtesy"

Airplane Flying Handbook, Quartering Headwind
Figure 4: Airplane Flying Handbook,
Quartering Headwind

Communications:

  • A low visibility taxi plan will exist giving the pilot additional instructions when the RVR is less than 1,200' and again in operations less than 600' RVR
  • Do not switch frequencies while taxiing, in case ground needs to contact you
  • Auto-switch tower when approaching the hold short to monitor traffic
  • If you have just cleared a runway and are looking to taxi, call with intentions as appropriate
    • ATC: "[Agency] Ground, [Callsign], clear of [Runway] at [Location], taxi to [Location]"
Airplane Flying Handbook, Surface Area Most Affected By Wind
Figure 5: Airplane Flying Handbook,
Surface Area Most Affected By Wind

Exiting the Runway:

  • Exit without delay at the first available taxiway or as instructed
  • All parts of the aircraft must be across the hold short line to be considered off the runway
  • Contact ground when directed by tower

Dangers:

  • Personnel must always be aware of the dangers associated with moving surfaces
  • Rotor wash created by the blades of a rotary-winged aircraft or thrust from the exhaust section of a fixed-winged aircraft may cause severe personnel injury
  • The proper safety equipment must always be worn when working on flight decks and flight lines
  • IT IS THE PILOT'S RESPONSIBILITY TO SEE AND AVOID ON THE TAXIWAY AS WELL


Tailwheel Considerations:

  • Aircraft with conventional landing gear (tailwheel/draggers) aircraft have special considerations that are unique to them
  • Ground Loop:

    • The center of gravity of a tailwheel aircraft is behind the cockpit which can cause instability during taxi
    • Make smooth inputs on the controls and be mindful that the center of gravity is not allowed to get to the side of the aircraft with enough momentum to carry it around
    • Once a ground loop has started there is no way to get out of it until it has run its course
    • In the interest of avoiding obstacles or staying on a paved surface however, differential breaking with the inside break will tighten the loop
  • Taxi Speed:

    • While speed can be a contributing factor to ground loops, it is also necessary to maintain positive control
    • If the aircraft is taxiing too fast, and breaks are applied too firmly, the tail can raise causing the tailwheel to lose effectiveness while simultaneously causing the propeller to move closer to the ground
    • If the tail comes up high enough, the pilot may experience a propeller, or "prop" strike
Airplane Flying Handbook, Standard Hand And Arm Signals
Figure 6: Airplane Flying Handbook, Standard Hand And Arm Signals

Hand Signals:

  • Flight Personnel are utilized on many aircraft ramps to direct traffic in an orderly fashion in accordance with local procedures
  • General Signals:

    • Affirmative:

      • Day: Thumbs up or head nod
      • Night: Flashlight moved vertically up-and-down repeatedly
    • Negative:

      • Day: Thumbs down or head shake
      • Night: Flashlight moved horizontally back-and-forth repeatedly
    • All Clear:

      • Day: One arm pointing up with the other pointing down
      • Night: Same signal as day, but with lights
    • Start Engine:

      • Day: Point to engine OR indicate engine number with fingers while making horizontal circular motion above head with other
      • Night: Same signal as day, but with lights
    • Proceed Straight Ahead:

      • Day: Hands gesture to come closer
      • Night: Same signal as day, but with lights
    • Pull Chocks:

      • Day: Move arms outward with thumbs pointed outward
      • Night: Same signal as day, but with lights
    • Turns:

      • Day: The direction of turn is indicated by that arm pointing downward while the other gestures to come closer
      • Night: Same signal as day, but with lights
    • Flagman Directs Pilot:

      • Day: Flagman holds hands in air to catch the pilot's attention
      • Night: Same signal as day, but with lights
    • Slow Down:

      • Day: With palms facing down, arms are moved up and down at side
      • Night: Same signal as day, but with lights
    • Insert Chocks:

      • Day: Move arms inward with thumbs pointed inward
      • Night: Same signal as day, but with lights
    • Cut Engine:

      • Day: A cutting motion with a flat palm is made across neck
      • Night: Same signal as day, but with lights
    • Stop:

      • Day: Arms are crossed with closed fist
      • Night: Same signal as day, but with lights
    • Clarify:

      • Day: Hand cupped behind ear as if listening
      • Night: None
    • Wait:

      • Day: Hand held up, palm toward pilot
      • Night: None
    • Ignore Last Signal:

      • Day: Hand waved back and forth in an erasing motion in front of face, with palm turned forward
      • Night: Trace of letter N, given by external light
    • Numbers:

      • Day:
        • Fingers held vertically indicate 1 through 5
        • Fingers held horizontally indicate 6 through 9
        • A clenched fist indicates zero
      • Night: None
    Airplane Flying Handbook, Standard Hand And Arm Signals
    Figure 6: Airplane Flying Handbook, Standard Hand And Arm Signals

Case Studies:

  • NTSB Identification: MIA01LA034 The National Transportation Safety Board determines the probable cause(s) of this accident to be: The student pilot's failure to maintain a visual look out while transitioning from the active runway to a taxiway resulting in an on-ground collision with a taxiway sign

Conclusion:

  • ATC clearances or instructions pertaining to taxiing are predicated on known traffic and known physical airport conditions
    • Since "the pilot-in-command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft" the pilot should obtain clarification of any clearance or instruction which is not understood
  • Therefore, it is important that pilots clearly understand the clearance or instruction
  • Although an ATC clearance is issued for taxiing purposes, when operating in accordance with the CFRs, it is the responsibility of the pilot to avoid collision with other aircraft
  • Be familiar with and comply with all airport markings and signs
  • When it comes to hand and arm signals, variations may exist
    • If any questions come up while taxiing, stop, and try to get clarification before proceeding

References: