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Holdover Time (HOT) Tables

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Category: Ground Operations Ground Operations
Content source: SKYbrary About SKYbrary
Content control: EUROCONTROL EUROCONTROL

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Description

Aircraft Ground De/Anti Icing Holdover Time (HOT) tables are approved by the SAE G-12 Committee are issued each year prior to the northern winter season.

These are then reviewed by AEA, FAA, and TC (Transport Canada) who are the main practical sources of HOT information and each issues their own version of the HOT Tables and associated support publications independently of each other and SAE. The generic changes from one season to the next are usually relatively few. However, in recent years, issues with residues from thickened fluids have been the main driver for the appearance of product-specific HOT tables, which are increasingly used by operators.

Other "official" sources sometimes publish HOT which are then left as "current" when they cease to be the latest versions. The effect of such out of date information being still accessible has resulted in many Operations Manuals being out of date on this critical safety subject.

In recent years, several companies have been developing systems that measure precipitation rate in real-time. These systems, referred to as liquid water equivalent systems (LWES), can be used by check-time determination systems (CTDS) and holdover time determination systems (HOTDS) to calculate more precise holdover times than can be obtained from the HOT Tables. They do this by using the weather data they collect as the input to the underlying assumptions employed in calculating the times in the HOT Tables.

Association of European Airlines (AEA)

  • The two regularly updated AEA Guides on the subject are:
    1. "Recommendations for De-Icing/Anti-Icing Aeroplanes on the Ground" (Edition 28 of this guide was published in July 2013) and
    2. "Recommendations and Background Information for De-Icing/Anti-Icing Aeroplanes on the Ground" (Edition 10 of this guide was published in August 2013)

Transport Canada (TC)

Federal Aviation Administration (FAA)

As a result of the development of LWES, CTDS and HOTDS, the FAA is making the regression coefficients and equations underlying the holdover time tables available to users:

Related Articles

Accident Reports

Accidents and Incidents resulting from airframe icing and problems with anti-icing fluids:

  • B763, Manchester UK, 1998 (GND FIRE) (On 25th November 1998, baggage containers on a B767, moved in flight causing damage to a cabin floor beam and damage to the standby system power supply cable causing electrical arcing. The aircraft landed safely at Manchester, UK, and the damage was only discovered during unloading.)
  • B738 / B738, Seville Spain, 2012 (GND HF) (On 13 April 2012 a Boeing 737-800 being taxied off its parking stand for a night departure by the aircraft commander failed to follow the clearly and correctly marked taxi centrelines on the well-lit apron and instead took a short cut towards the taxiway centreline which resulted in the left winglet striking the left horizontal stabiliser and elevator of another Ryanair aircraft correctly parked on the adjacent stand causing damage which rendered both aircraft unfit for flight. The pilot involved was familiar with the airport and had gained almost all his flying experience on the accident aircraft type.)
  • A333, Hong Kong China, 2010 (LOC RE GND FIRE) (On 13 April 2010, a Cathay Pacific Airbus A330-300 en route from Surabaya to Hong Kong experienced difficulty in controlling engine thrust. As these problems worsened, one engine became unusable and a PAN and then a MAYDAY were declared prior to a successful landing at destination with excessive speed after control of thrust from the remaining engine became impossible. Emergency evacuation followed after reports of a landing gear fire. Salt water contamination of the hydrant fuel system at Surabaya after alterations during airport construction work was found to have led to the appearance of a polymer contaminant in uplifted fuel.)
  • B744 / A321, London Heathrow UK, 2004 (GND HF) (On 23 March 2004, an out of service British Airways Boeing 747-400, under tow passed behind a stationary Airbus A321-200 being operated by Irish Airline Aer Lingus on a departing scheduled passenger service in good daylight visibility and the wing tip of the 747 impacted and seriously damaged the rudder of the A321. The aircraft under tow was cleared for the towing movement and the A321 was holding position in accordance with clearance. The towing team were not aware of the collision and initially, there was some doubt in the A321 flight deck about the cause of a ‘shudder’ felt when the impact occurred but the cabin crew of the A321 had felt the impact shudder and upon noticing the nose of the 747 appearing concluded that it had struck their aircraft. Then the First Officer saw the damaged wing tip of the 747 and informed ATC about the possible impact. Later another aircraft, positioned behind the A321, confirmed the rudder damage. At the time of the collision, the two aircraft involved were on different ATC frequencies.)
  • B738/B763, Barcelona Spain, 2011 (GND HF) (On 14 April 2011, a Ryanair Boeing 737-800 failed to leave sufficient clearance when taxiing behind a stationary Boeing 767-300 at Barcelona and the 737 wingtip was in collision with the horizontal stabiliser of the 767, damaging both. The 767 crew were completely unaware of any impact but the 737 crew realised the ‘close proximity’ but dismissed a cabin crew report that a passenger had observed a collision. Both aircraft completed their intended flights without incident after which the damage was discovered, that to the 767 requiring that the aircraft be repaired before further flight.)
  • … further results

warning.png"Ground de/anti icing" is not in the list of possible values (Taxiway collision, On gate collision, Aircraft / Aircraft conflict, Aircraft / Person conflict, Aircraft / Vehicle conflict, Aircraft / Object or Structure conflict, ATC clearance error, Ground de/anti icing ineffective, Ground de/anti icing not available, Failure to De/anti Ice, Jet Blast / Prop wash, Surface Friction, Towed aircraft involved, Aircraft Push Back, Incorrect Parking Position, Airbridge Positioning, Both objects moving, Wingtip clearance, Centreline obscured, Accepted ATC clearance not followed, Surface Lighting control, Hold Loading, Passenger Loading, Cargo Loading, Fuel Loading, Dangerous Goods, Engine Ground Running, Engine Powered Systems Test, No Flight Crew on Board, Charting Error) for this property.

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