If you wish to contribute or participate in the discussions about articles you are invited to join SKYbrary as a registered user
Holdover Time (HOT) Tables
- 1 Description
- 2 Related Articles
- 3 Accident and Incident Reports
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 The effect of such out of date information being still accessible has resulted in many Operations Manuals being out of date on this critical safety subject.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:
- "Recommendations for De-Icing/Anti-Icing Aeroplanes on the Ground" (Edition 29 of this guide was published in July 2014) and
- "Recommendations and Background Information for De-Icing/Anti-Icing Aeroplanes on the Ground" (Edition 11 of this guide was published in August 2014)
- The AEA HOT Tables are found in Annex A to the Recommendations for De-Icing/Anti-Icing of Aircraft on the Ground
Transport Canada (TC)
- 2014/2015 Transport Canada HOT tables
- Transport Canada: Guidelines for Aircraft Ground Icing Operations amendments to which can be found with the latest edition of the HOT tables issued prior to each winter season.
Federal Aviation Administration (FAA)
Accident and Incident Reports
Accidents and Incidents resulting problems with de/anti-icing:
Failure to de/anti ice when facilities available
- CL60, Birmingham UK, 2002 (GND LOC HF FIRE) (On 4 January 2002, a Challenger 604 operated by Epps Air Service, crashed on takeoff from Birmingham, UK, following loss of control due to airframe icing.)
Ground de/anti icing not available
- PRM1, vicinity Annemasse France, 2013 (LOC HF FIRE) (On 4 March 2013, a Beechcraft Premier 1A stalled and crashed soon after take off from Annemasse. The Investigation concluded that the stall and subsequent loss of control was attributable to frozen deposits on the wings which the professional pilot flying the privately-operated aircraft had either not been aware of or had considered insignificant. It was noted that the aircraft had been parked outside overnight and that conditions had favoured frost formation. The presence of a substantial quantity of cold-soaked fuel had favoured frost formation. The presence of a substantial quantity of cold-soaked fuel in the wing tanks overnight was also noted.)
Ground de/anti icing ineffective
- AT72, vicinity Tyumen Russian Federation, 2012 (LOC GND HF FIRE) (On 2 April 2012, the crew of a UT Air ATR72-210 which had just taken off from Tyumen lost control of the aircraft and it crashed and caught fire killing or seriously injuring all occupants. The subsequent Investigation attributed the accident to the decision of the aircraft commander to take off without prior ground de icing when frozen deposits had accumulated on the airframe. However, a wide ranging systemic context for this was found, including ineffective regulatory requirements and a dysfunctional SMS at UT Air.)
- B463, en-route, South of Frankfurt Germany, 2005 (LOC GND) (On 12 March 2005, a BAe-146-300 climbing out of Frankfurt experienced a loss of elevator control authority and an uncommanded descent at up to 4500 fpm whilst in a nose high pitch attde which was eventually arrested and subsequently attributed to the freezing of re-hydrated ground de/anti-ice fluid residues. The crew decided to continue to their originally-intended destination since it offered the prospect of more favourable weather conditions for landing. The aircraft later landed at Stuttgart after using elevator trim to control pitch attitude.)
- B732, vicinity Washington National DC USA, 1982 (LOC HF WX GND) (On 13 January 1982, an Air Florida Boeing 737-200 took off in daylight from runway 36 at Washington National in moderate snow but then stalled before hitting a bridge and vehicles and continuing into the river below after just one minute of flight killing most of the occupants and some people on the ground. The accident was attributed entirely to a combination of the actions and inactions of the crew in relation to the prevailing adverse weather conditions and, crucially, to the failure to select engine anti ice on which led to over reading of actual engine thrust.)
- B733, Birmingham UK, 2009 (GND HF RE) (On the morning of 6 February 2009, a Boeing 737-300 being operated by bmibaby was departing from Birmingham for Edinburgh on a scheduled passenger flight and the crew had had the aircraft de-iced on the gate prior to departure. The stabiliser trim was not set at the usual time due to the ongoing de-icing procedure and the omission was not noticed after start because the crew became preoccupied with the flap setting. The aircraft started its takeoff run with the incorrect stabiliser trim setting and the First Officer, the designated PF, was subsequently unable to raise the aircraft nose at VR. The Captain then decided to reject the takeoff. The thrust levers were closed at 155 kts, considerably in excess of V1, and the aircraft stopped on the runway without further incident.)
- B738, vicinity Kittilä, Finland 2012 (LOC GND HF) (On 26 December 2012, a Norwegian Air Shuttle Boeing 737-800 intercepting the ILS GS at Kittilä with the AP engaged experienced an uncommanded pitch up in IMC. Crew response did not prevent rapid development of a very high nose up attitude and, as airspeed dropped rapidly whilst climbing, stick shaker activation occurred. Recovery from the upset was eventually achieved and there was no recurrence. The Investigation is continuing but initial findings are that the normal operation of one of the elevator PCUs had been compromised by ground de-ice fluid residue and that all Boeing 737 variants may be vulnerable.)
Unintended side effects of ground de/anti icing
- A320, en-route, Kalmar County Sweden, 2009 (GND FIRE HF) (On 2 March 2009, an Airbus A320-200 being operated by Wizz Air Hungary on a scheduled passenger flight from Stockholm Vasteras to Poznan was in the cruise at night when the flight crew detected an unfamiliar smell on the flight deck and decided to guard against possible incapacitation by donning their oxygen masks from time to time for the remainder of the flight. There was some evidence of the same effect in the passenger cabin. The flight was completed without further consequences and none of the 85 occupants was affected except temporarily.)
Ground de/anti ice fluid residue effect on flight controls
- ATP, Helsinki Finland, 2010 (RE AW GND) (On 11 January 2010, a British Aerospace ATP being operated by West Air Sweden on a cargo flight from Helsinki to Copenhagen with only the two operating flight crew on board at night could not be rotated for take off on runway 22R. The ensuing rejected take off in normal ground visibility was achieved within the available runway length and the aircraft was undamaged and returned to the apron.)