Bollocks - & I wonder?
Mr Boyle: "There have actually been three applications over the last decade to restore the 10 knots—or to increase the tailwind limit. Following its removal, Airservices applied to CASA for 10 knots. That was rejected. BAC followed up with an application for 10 knots that was rejected around 2017. In 2022, post-opening—we now have more data on the operation of the runways—the decision was made to submit a safety case for seven knots, as that was seen as being a compromise between the five and the 10. We believe we would still get improvement in SODPROPS from seven knots. The safety case was actually prepared and submitted by Airservices, and they did consult widely. There may have been some confusion this morning because Aus ALPA were consulted on the safety case twice in February 2022. They made 11 individual submissions, all in opposition to the safety case. But they were certainly" etc.— Bollocks..........
I wonder? - Is it a waste of time and energy to even try to explain, in 'lay' language to office bound bubble dwellers why there are very sound safety/ legal and operationally based needs for a 'maximum' tail wind 'standard. The subject is not overly complicated, but requires a modicum of common (or garden) sense. I shall, with apologises to those who do actually 'fully' understand the 'safety' implications, dip my thumb nail into the tar pot and construe. (Stop here if you get it)....;
First let us paint a picture; surrounding our aerodrome there is some rising terrain; nothing spectacular; just rising terrain ahead, Cairns in Qld - for example.
For ease of 'numbers' lets use a working example of 120 knots (222.21 kph). So, from the beginning of the runway to overhead the terrain; we have 10 miles to work with. Basically (*) to get an aircraft 'airborne'; it requires airflow, relative to 'over the wings' - forward speed less than tail wind speed is useless for 'lift'. Relative to wing performance airflow, is provided by the power plant (engines); if there is a 10 knot 'headwind', then then, insofar as 'wind over wing' the engines are 'ahead' and, bonus, the opposing 'head wind' slows the aircraft speed 'over the ground' - so it is a win win. A little more time before reaching the terrain i.e. a better height to distance ratio. Clearly desirable when confronting 'rising terrain' ahead. As the wind direction moves left or right from straight ahead; this 'achieved' climb gradient equation reduces - this is a 'cross-wind' situation - the climb gradient numbers don't change very much - but; there is a reduction and a slight increase in the distance of runway used. Once again, not critical, but worthy of consideration when factoring take off weights and terrain clearance.
Routine stuff; done a million times everyday - world wide; very nearly safe as houses. Nearly that is until something goes pear shaped, and Murphy is dealt a hand. There are many opportunities for this to happen; but of greatest concern must be the 'engine failure' case- ranked only second to structural failure - think of Sully and the Sea Gulls. An engine failure at the most critical juncture during a take off is always a major consideration and allowances are made (reduced weight = reduced payload) to accommodate the event; this is a 'cost' to operator factor which is universally enforced; part of the game. With an 'engine out' - a 'head wind' is an essential element; the climb gradient (height for distance) is severely reduced. Once gain, this is all factored into the calculations to ensure, as far as possible, that aircraft and terrain are properly and legally separated. Only makes legal, operational and common sense.
The 'handy' 10 knot 'headwind' for take off becomes a critical part of the 'safety' equation. A 10 knot tail wind is liability - for starters; the aircraft must be going forward at 10 knots before the over wing airflow begins to create the essential 'lift'. The 'lift' from the wing is generated by the 'relative' (front to rear airflow) NOT the speed the aircraft is travelling at. Zero lift at 10 knots indicated.
You can see the quandary - it is always a compromise even with a headwind. Tail wind take off demands the aircraft 'get ahead' of the ambient wind before the wings can generate the essential 'lift'. This 'reduces' the useful runway distance available distance required (to reach 10 knots); which naturally takes the aircraft closer to obstacles ahead and reduces the climb gradient ratio.
All logical, factored and 'accommodated' within 'safe' boundaries before take off is initiated. So far so good, all neat and tidy, working within 'fixed' parameters, even down to the accurately calculated margins:based on the critical engine failure case (for transport aircraft).
So what's the fuss about 'tail wind' operations? The internationally adopted 'Five Knot' standard is a 'considered' maximum' weighted on the side of 'a wide range of non quantifiable variables. Amongst these, consideration is given 'averages' things like the performance of engines which are not brand new, air-frames which have covered many miles, completed many take off and landings, handled by many different pilots. So, yes, there is a 'conservative' element within the equations; and, rightly so. Exceptions? operationally - yes: but mostly approved, fully 'justified' and with limitations applied - not all aerodromes are 'equal'.
Which brings us to landing the aircraft at the other end - this, believe it or not, has an increased 'risk' element; and is - with a 'tail wind component - probably the part of the flight which has the least 'predictable' outcome. There are some situations when there is a strong, gusty cross wind, 'quartering' behind; quite often with associated turbulence. Flight crew can manage these conditions; but - (always a but) the distance required for the landing run is, once again, carefully calculated. Predicted on the aircraft weight, producing a 'speed' margin and based on using a specific 'area' of the runway (touch down zone). Should the aircraft stray outside of these parameters, then 'safety' (legal and operational) is compromised. Not just in terms of running off the end of the runway; this is the least likely result. The 'danger' zone is where the aircraft is 'dirty' - landing flap, engines spooled down, landing gear extended - low energy and high workload to deal with should (a) the final approach need to be terminated at low level and an engine fails during the process. This is the highest category of risk. Aye; Mathematically low probability, but it has, does and will happen again. This is where the insidious, inherent dangers of allowing operations with increased tail wind component truly reside. The overshoot may be masterfully managed; low, slow and 'dirty' - engine failure - massif (big) reduction in climb gradient - rocks and trees and other stuff - much closer now- Tick Tock and Murphy rules.
ICAO standard is a 5 knot maximum; world wide.
“Aviation in itself is not inherently dangerous. But to an even greater degree than the sea, it is terribly unforgiving of any carelessness, incapacity or neglect.”
Believe it or not; this time honoured, many times proven adage applies to governing bodies, airport operators and idiot air traffic managers who think they, in pursuit of the holy dollar, can, with impunity decide they know better and are prepared to roll the dice. The polite response is a firm 'No', not on my command; the alternative (recommended) response is 'Piss off - and boil your bottom' or word to that effect.
With my sincere apologies to those actually know what they are talking about:-
Toot - toot.
Mr Boyle: "There have actually been three applications over the last decade to restore the 10 knots—or to increase the tailwind limit. Following its removal, Airservices applied to CASA for 10 knots. That was rejected. BAC followed up with an application for 10 knots that was rejected around 2017. In 2022, post-opening—we now have more data on the operation of the runways—the decision was made to submit a safety case for seven knots, as that was seen as being a compromise between the five and the 10. We believe we would still get improvement in SODPROPS from seven knots. The safety case was actually prepared and submitted by Airservices, and they did consult widely. There may have been some confusion this morning because Aus ALPA were consulted on the safety case twice in February 2022. They made 11 individual submissions, all in opposition to the safety case. But they were certainly" etc.— Bollocks..........
I wonder? - Is it a waste of time and energy to even try to explain, in 'lay' language to office bound bubble dwellers why there are very sound safety/ legal and operationally based needs for a 'maximum' tail wind 'standard. The subject is not overly complicated, but requires a modicum of common (or garden) sense. I shall, with apologises to those who do actually 'fully' understand the 'safety' implications, dip my thumb nail into the tar pot and construe. (Stop here if you get it)....;
First let us paint a picture; surrounding our aerodrome there is some rising terrain; nothing spectacular; just rising terrain ahead, Cairns in Qld - for example.
For ease of 'numbers' lets use a working example of 120 knots (222.21 kph). So, from the beginning of the runway to overhead the terrain; we have 10 miles to work with. Basically (*) to get an aircraft 'airborne'; it requires airflow, relative to 'over the wings' - forward speed less than tail wind speed is useless for 'lift'. Relative to wing performance airflow, is provided by the power plant (engines); if there is a 10 knot 'headwind', then then, insofar as 'wind over wing' the engines are 'ahead' and, bonus, the opposing 'head wind' slows the aircraft speed 'over the ground' - so it is a win win. A little more time before reaching the terrain i.e. a better height to distance ratio. Clearly desirable when confronting 'rising terrain' ahead. As the wind direction moves left or right from straight ahead; this 'achieved' climb gradient equation reduces - this is a 'cross-wind' situation - the climb gradient numbers don't change very much - but; there is a reduction and a slight increase in the distance of runway used. Once again, not critical, but worthy of consideration when factoring take off weights and terrain clearance.
Routine stuff; done a million times everyday - world wide; very nearly safe as houses. Nearly that is until something goes pear shaped, and Murphy is dealt a hand. There are many opportunities for this to happen; but of greatest concern must be the 'engine failure' case- ranked only second to structural failure - think of Sully and the Sea Gulls. An engine failure at the most critical juncture during a take off is always a major consideration and allowances are made (reduced weight = reduced payload) to accommodate the event; this is a 'cost' to operator factor which is universally enforced; part of the game. With an 'engine out' - a 'head wind' is an essential element; the climb gradient (height for distance) is severely reduced. Once gain, this is all factored into the calculations to ensure, as far as possible, that aircraft and terrain are properly and legally separated. Only makes legal, operational and common sense.
The 'handy' 10 knot 'headwind' for take off becomes a critical part of the 'safety' equation. A 10 knot tail wind is liability - for starters; the aircraft must be going forward at 10 knots before the over wing airflow begins to create the essential 'lift'. The 'lift' from the wing is generated by the 'relative' (front to rear airflow) NOT the speed the aircraft is travelling at. Zero lift at 10 knots indicated.
You can see the quandary - it is always a compromise even with a headwind. Tail wind take off demands the aircraft 'get ahead' of the ambient wind before the wings can generate the essential 'lift'. This 'reduces' the useful runway distance available distance required (to reach 10 knots); which naturally takes the aircraft closer to obstacles ahead and reduces the climb gradient ratio.
All logical, factored and 'accommodated' within 'safe' boundaries before take off is initiated. So far so good, all neat and tidy, working within 'fixed' parameters, even down to the accurately calculated margins:based on the critical engine failure case (for transport aircraft).
So what's the fuss about 'tail wind' operations? The internationally adopted 'Five Knot' standard is a 'considered' maximum' weighted on the side of 'a wide range of non quantifiable variables. Amongst these, consideration is given 'averages' things like the performance of engines which are not brand new, air-frames which have covered many miles, completed many take off and landings, handled by many different pilots. So, yes, there is a 'conservative' element within the equations; and, rightly so. Exceptions? operationally - yes: but mostly approved, fully 'justified' and with limitations applied - not all aerodromes are 'equal'.
Which brings us to landing the aircraft at the other end - this, believe it or not, has an increased 'risk' element; and is - with a 'tail wind component - probably the part of the flight which has the least 'predictable' outcome. There are some situations when there is a strong, gusty cross wind, 'quartering' behind; quite often with associated turbulence. Flight crew can manage these conditions; but - (always a but) the distance required for the landing run is, once again, carefully calculated. Predicted on the aircraft weight, producing a 'speed' margin and based on using a specific 'area' of the runway (touch down zone). Should the aircraft stray outside of these parameters, then 'safety' (legal and operational) is compromised. Not just in terms of running off the end of the runway; this is the least likely result. The 'danger' zone is where the aircraft is 'dirty' - landing flap, engines spooled down, landing gear extended - low energy and high workload to deal with should (a) the final approach need to be terminated at low level and an engine fails during the process. This is the highest category of risk. Aye; Mathematically low probability, but it has, does and will happen again. This is where the insidious, inherent dangers of allowing operations with increased tail wind component truly reside. The overshoot may be masterfully managed; low, slow and 'dirty' - engine failure - massif (big) reduction in climb gradient - rocks and trees and other stuff - much closer now- Tick Tock and Murphy rules.
ICAO standard is a 5 knot maximum; world wide.
“Aviation in itself is not inherently dangerous. But to an even greater degree than the sea, it is terribly unforgiving of any carelessness, incapacity or neglect.”
Believe it or not; this time honoured, many times proven adage applies to governing bodies, airport operators and idiot air traffic managers who think they, in pursuit of the holy dollar, can, with impunity decide they know better and are prepared to roll the dice. The polite response is a firm 'No', not on my command; the alternative (recommended) response is 'Piss off - and boil your bottom' or word to that effect.
With my sincere apologies to those actually know what they are talking about:-
Toot - toot.