1.67 rule
Joined: Dec 2002
Posts: 2,775
Likes: 353
From: UK
Re # 20 PBL “the flight crew's decisions were appropriate in light of the information they were given”
As an example see http://www.skybrary.aero/bookshelf/books/1248.pdf
Selected extracts –
The landing was planned based on a dry runway with good braking action.
Based on the received information the crew did not expect any problems related to the weather or runway conditions.
The aircraft landed with 140 KIAS from a Vapp (VLS) of 147 KIAS. The speed was based on the correct Vref for the actual landing mass and increased 5 kt for Auto Thrust and 5 kt for icing conditions. This is in line with the company's standard landing procedures but is not optimal on contaminated and slippery runways.
The aircraft landed long with a soft touchdown … approx 3 kt tailwind … contaminated runway.
In hindsight – to be used for learning and not for blame, there could have been some mitigating activity.
“The landing was planned based on a dry runway with good braking action.” Typically, factored landing data provides a margin for the normal day-to-day variability in height, speed, touchdown point, etc (but not all at once), and a choice of braking level. i.e. there is a safety margin which provides the basis of a mindset involving a normal operation – even complacency.
“Three minutes before touchdown the crew were told that the runway was contaminated with 8 mm of wet snow and a braking action of 32-33-31 (MEDIUM). The crew made an assessment and decided that they were able to land with MEDIUM Braking Action… , it did not give the crew cause for concern with regard friction.”
If this assessment was based on contaminated landing data which was based on CS AMC 25.1591 (approx page 710 in Am 9) then there may not have been any effective safety margin, even with the factors required by EU OPS-1.520 (b).
The published contaminated data may assume a threshold speed = Vref, touchdown 93% of Vref, 7 sec flare time, use of reverse thrust, etc, etc, and maximum braking.
Therefore it would be necessary for the crew to ‘reprogram’ the mindset from a normal – ‘data checked = OK’, to a contaminated landing special procedures mindset (speed / touchdown accuracy, max brake, full reverse) or even consider diverting.
We have opportunity to learn from the unfortunate culmination of factors experienced by others; we should not overlook such opportunities.
As an example see http://www.skybrary.aero/bookshelf/books/1248.pdf
Selected extracts –
The landing was planned based on a dry runway with good braking action.
Based on the received information the crew did not expect any problems related to the weather or runway conditions.
The aircraft landed with 140 KIAS from a Vapp (VLS) of 147 KIAS. The speed was based on the correct Vref for the actual landing mass and increased 5 kt for Auto Thrust and 5 kt for icing conditions. This is in line with the company's standard landing procedures but is not optimal on contaminated and slippery runways.
The aircraft landed long with a soft touchdown … approx 3 kt tailwind … contaminated runway.
In hindsight – to be used for learning and not for blame, there could have been some mitigating activity.
“The landing was planned based on a dry runway with good braking action.” Typically, factored landing data provides a margin for the normal day-to-day variability in height, speed, touchdown point, etc (but not all at once), and a choice of braking level. i.e. there is a safety margin which provides the basis of a mindset involving a normal operation – even complacency.
“Three minutes before touchdown the crew were told that the runway was contaminated with 8 mm of wet snow and a braking action of 32-33-31 (MEDIUM). The crew made an assessment and decided that they were able to land with MEDIUM Braking Action… , it did not give the crew cause for concern with regard friction.”
If this assessment was based on contaminated landing data which was based on CS AMC 25.1591 (approx page 710 in Am 9) then there may not have been any effective safety margin, even with the factors required by EU OPS-1.520 (b).
The published contaminated data may assume a threshold speed = Vref, touchdown 93% of Vref, 7 sec flare time, use of reverse thrust, etc, etc, and maximum braking.
Therefore it would be necessary for the crew to ‘reprogram’ the mindset from a normal – ‘data checked = OK’, to a contaminated landing special procedures mindset (speed / touchdown accuracy, max brake, full reverse) or even consider diverting.
We have opportunity to learn from the unfortunate culmination of factors experienced by others; we should not overlook such opportunities.
Joined: Aug 2005
Posts: 97
Likes: 0
From: Europe
1.67 - Civil Air Regulations 1942
IGh
Good job finding the source of 1.67 factor.
Is the CIVIL AIR REGULATIONS, PART 61 of 1942, and the CIVIL AERONAUTICS MANUAL 04-T of 1944 available through the Internet?
If not, I would appreciate if I could recieve a copy in a PM. at least the four and a half pages related to landing and take-off and the related pages in the 1944 CIVIL AERONAUTICS MANUAL 04-T
Do you also have the 16 lines in the 1939 American Civil Air Regulations available?
Certainly the new code is far more complex than the old. In 1939 the specifications with respect to the landing and take-off performance of aircraft consumed only 16 lines of the American Civil Air Regulations. They now occupy 41/2 pages.
Tribo
Good job finding the source of 1.67 factor.
Is the CIVIL AIR REGULATIONS, PART 61 of 1942, and the CIVIL AERONAUTICS MANUAL 04-T of 1944 available through the Internet?
If not, I would appreciate if I could recieve a copy in a PM. at least the four and a half pages related to landing and take-off and the related pages in the 1944 CIVIL AERONAUTICS MANUAL 04-T
Do you also have the 16 lines in the 1939 American Civil Air Regulations available?
Certainly the new code is far more complex than the old. In 1939 the specifications with respect to the landing and take-off performance of aircraft consumed only 16 lines of the American Civil Air Regulations. They now occupy 41/2 pages.
Tribo
Joined: May 2020
Posts: 14
Likes: 0
From: dublin
Very well Described Old Smokey. 👍🏻 😊
Last edited by jondoyle; 21st May 2024 at 12:07. Reason: Reduced size of original quote
Joined: Dec 2002
Posts: 2,775
Likes: 353
From: UK
Current orations, post TALPA, using Operational Landing Distances (OLD), should not require use of factored landing distance as the primary data source.
Landing performance for pre landing assessment should be based on EU-OPS, CS 25.1592 or AC 25-32 (EASA operational requirement, FAA recommendation).
The recently amended AC 91-79B publishes factors to estimate landing distance if OLD are not available; the factors range 1.67 to 5.1 according to reported braking action and aircraft type ( lines … a matrix in the sand ). The basis of these is the ICAO Manual of Aircraft Performance, doc 10064.
Note the amended Chapt 3 (AC 91) re use of most adverse report of braking action or expected conditions, the 15% minimum factor applied to OLD may be inadequate in some conditions; plan for the worst case conditions i.e. RCR - 1
Also note tech assumptions about braking performance ("… to create a reasonably conservative relationship between this engineering scale and a set of standardized descriptions of wet and contaminated condition") and validity of the performance model ("… there may be instances where the model may not apply values conservative enough for TOA landing assessments.)
The FAA places greater reliance on PIREPs (PBAR) than EASA, Chapt 4.
There is extensive small print to fall foul of. e.g. " Braking action reports should be based solely on the wheel braking component of the aircraft’s deceleration. Pilots need to understand that stopping results do not necessarily correlate to braking action. The effects of aerodynamic forces, while beneficial to stopping performance, should not be considered when making a braking action report. For turbojets, the effect of reverse thrust should not be considered. Likewise, for propeller driven airplanes, the effect of reverse pitch should not be considered."
and much more,
'Aircraft Landing Performance and Runway Excursions Mitigation'
https://www.faa.gov/documentLibrary/...91-79B_FAA.pdf
,
Landing performance for pre landing assessment should be based on EU-OPS, CS 25.1592 or AC 25-32 (EASA operational requirement, FAA recommendation).
The recently amended AC 91-79B publishes factors to estimate landing distance if OLD are not available; the factors range 1.67 to 5.1 according to reported braking action and aircraft type ( lines … a matrix in the sand ). The basis of these is the ICAO Manual of Aircraft Performance, doc 10064.
Note the amended Chapt 3 (AC 91) re use of most adverse report of braking action or expected conditions, the 15% minimum factor applied to OLD may be inadequate in some conditions; plan for the worst case conditions i.e. RCR - 1
Also note tech assumptions about braking performance ("… to create a reasonably conservative relationship between this engineering scale and a set of standardized descriptions of wet and contaminated condition") and validity of the performance model ("… there may be instances where the model may not apply values conservative enough for TOA landing assessments.)
The FAA places greater reliance on PIREPs (PBAR) than EASA, Chapt 4.
There is extensive small print to fall foul of. e.g. " Braking action reports should be based solely on the wheel braking component of the aircraft’s deceleration. Pilots need to understand that stopping results do not necessarily correlate to braking action. The effects of aerodynamic forces, while beneficial to stopping performance, should not be considered when making a braking action report. For turbojets, the effect of reverse thrust should not be considered. Likewise, for propeller driven airplanes, the effect of reverse pitch should not be considered."
and much more,
'Aircraft Landing Performance and Runway Excursions Mitigation'
https://www.faa.gov/documentLibrary/...91-79B_FAA.pdf
,
Last edited by safetypee; 21st May 2024 at 14:30.
