A ramble; definitely not for the professionals.
To oblige a polite request to ‘simplify’ some technical matters the following ‘potted’ version of ‘why’ there is problem with building in close proximity to runways, this is my humble offering.
Stuck, for moment without serial number specific data; and, hindered by a lack of ‘solid’ exact detail of the ‘failure’ nature (gear box, FCU, etc.) we are only left with the flight path and ‘speed’ schedule to play with; oh and the ducking buildings (‘cept they didn’t oblige).
However in the general way of ‘discussion’ I managed to find my own ‘refamil’ notes, now a decade old; so don’t quote them as specific to ‘the’ aircraft in question’. There are three Be20 Aircraft Flight Manuals (AFM – legal tender) on the shelf here within easy reach of a long arm, so to begin to ‘ballpark’, let us take a peep at the AFM speed schedule. The Be20 offers ‘indicated airspeed’ in knots (KIAS) i.e. what’s on the speedo.
The aircraft minimum control speed air is slated at 86 KIAS. The “V” in the acronyms stands for ‘velocity’. So, Minimum Control Speed Air becomes Vmca. It is a complex notion for the layman to grasp, even many CASA inspectors have a problems grasping the ‘true' meaning of what it is and, importantly, how it is derived by test pilots under certifying test. So, take it that it is a speed below which the aircraft rudder runs out of ‘power’ to prevent the yaw induced when an engine quits. Think car tyre puncture, which way does the car go – yaw).
Next we find the ubiquitous and infamous “Blue line” speed, the Be20 has this speed settled at 121 KIAS. Known as the Single Engine Best Rate of Climb (SEBROC) noted as Vyse.
On each and every take off in an aircraft ln the Be20 class the aim is to persuade the beast to leave the earth at a speed much better than VMC 86 and to achieve SEBROC as quickly as possible – no brainer – right. It is an increase in speed of 35 knots (70 KpH).
Which leads us to ‘other’ options; the aircraft has a range of useful ‘speeds’. At the low end, the title Vx or Multi Engine Best Rate of Climb (MEBROC) 100 KIAS is available (most ‘up’ for least ‘forward). Followed by VSSE (Safe Single Engine) offered at 104 KIAS. Nominally the lowest speed at which an engine failure may simulated. The next speed ‘gate’ is 115 KIAS, known as Vxse, titled SEBAC, which is the Single Engine Best Angle of Climb. A handy speed to fly at when there are obstacles to clear and an engine has quit.
Next on the list Vyse at a mighty 121 KIAS is the SEBROC, great speed for going ‘up’ quickly if there are no obstacles ahead – distance 'to' - is not a problem.
Final gateway to nirvana – MEBROC; Multi Engine Best Rate of Climb, Vy 125 kIAS. Well done class. One last number to remember, normal cruise climb (comfortable angle) speed 160 KIAS.
Consider this; let’s call it a safe take off pathway, through ‘gates’; the first speed gate we must attend to is Vmca; pilots usually take a moment just before this speed to have a final look at the engine readouts. It is remarkably easy and very safe to ‘stop’ an aircraft of this ‘class’ in the 80 to 90 knot range if something is amiss; after this it becomes more difficult until it becomes unwise to attempt to stop at a higher speed (conditional). And so Gate 1 slides past all is well, now we need a ‘good’ speed to persuade the beast to leave the runway. Our friend Vx@100 seems to be a fair choice, so up we go, looking to accelerate to the lowest speed which will produce some climb performance; should an engine quit (airborne now runway gone). The easiest and quickest is Vxse 115, through that gate and the aircraft is now moving swiftly, the Vyse gate is behind in a heart beat and ‘cruise climb 160 KIAS is hot on its heels. Start to finish? What, perhaps 60 seconds. Stroll in the park. And so it is; until ‘something’ quits. To keep it simple, lets just lump the ‘quits’ compendium into one bucket and call it an engine failure.
Lets work backwards – say you are at 200 feet, 160 KIAS and climbing at 2000 feet per minute (FpM) and you go One Engine Inoperative (OEI); so what, it is an inconvenience and the paperwork is a nightmare; but you pedal it around and plonk it on the nearest suitable. Drinks all around.
Now, back to 200’. and you go OEI with 130 KIAS on the clock; problem. If you loose 5 knots, which is easy to do, you are back to a critical speed 125, provided you loose no more speed, then a performance climb to a safe height is possible. Should you go OEI at 125 KIAS the next safe speed is 121 for ‘climb performance’; it is terribly easy to loose those precious four or five knots; turbulence can rob you, slow reaction can rob you, incorrect technique can rob you of those precious few knots. But, if you go OEI below a single engine climb performance speed; you have a major problem.
The problem being that you need, indeed must, accelerate the aircraft to at least the lowest ‘climb’ speed. In order to achieve this, climbing must be put aside to avoid a further reduction in speed until the tombstone of Vmca appears on the clock. To accelerate at low level, OEI to a safe climb speed needs two essential elements; the most important of which is no obstacles at a greater height than you are. In short class, you need one essential element or the other to be available, preferably both, if you intend to get to the pub. Speed and height; Height and speed.
The King Air at Essendon had neither and failed to escape the clutches of the DFO.
There are serious questions to be answered related to the speed schedule; the aircraft was airborne with 116 KIAS ; only five knots shy of a performance climb speed and only one knot above the SEBAC speed. Why was there a progressive speed reduction to a terminal velocity of 108 KIAS instead of a level acceleration to a performance speed? Many ask why was the power not hauled off and the aircraft ‘dumped’ on the aerodrome. Sorry, far too many variables to say anything for sure.
To my Be20 qualified colleagues, I make my most sincere apologies for ‘brutalising’ and short hand handing the technicalities. “’twas a necessary evil M’luds”. MTF…..
Toot- toot.
To oblige a polite request to ‘simplify’ some technical matters the following ‘potted’ version of ‘why’ there is problem with building in close proximity to runways, this is my humble offering.
Stuck, for moment without serial number specific data; and, hindered by a lack of ‘solid’ exact detail of the ‘failure’ nature (gear box, FCU, etc.) we are only left with the flight path and ‘speed’ schedule to play with; oh and the ducking buildings (‘cept they didn’t oblige).
However in the general way of ‘discussion’ I managed to find my own ‘refamil’ notes, now a decade old; so don’t quote them as specific to ‘the’ aircraft in question’. There are three Be20 Aircraft Flight Manuals (AFM – legal tender) on the shelf here within easy reach of a long arm, so to begin to ‘ballpark’, let us take a peep at the AFM speed schedule. The Be20 offers ‘indicated airspeed’ in knots (KIAS) i.e. what’s on the speedo.
The aircraft minimum control speed air is slated at 86 KIAS. The “V” in the acronyms stands for ‘velocity’. So, Minimum Control Speed Air becomes Vmca. It is a complex notion for the layman to grasp, even many CASA inspectors have a problems grasping the ‘true' meaning of what it is and, importantly, how it is derived by test pilots under certifying test. So, take it that it is a speed below which the aircraft rudder runs out of ‘power’ to prevent the yaw induced when an engine quits. Think car tyre puncture, which way does the car go – yaw).
Next we find the ubiquitous and infamous “Blue line” speed, the Be20 has this speed settled at 121 KIAS. Known as the Single Engine Best Rate of Climb (SEBROC) noted as Vyse.
On each and every take off in an aircraft ln the Be20 class the aim is to persuade the beast to leave the earth at a speed much better than VMC 86 and to achieve SEBROC as quickly as possible – no brainer – right. It is an increase in speed of 35 knots (70 KpH).
Which leads us to ‘other’ options; the aircraft has a range of useful ‘speeds’. At the low end, the title Vx or Multi Engine Best Rate of Climb (MEBROC) 100 KIAS is available (most ‘up’ for least ‘forward). Followed by VSSE (Safe Single Engine) offered at 104 KIAS. Nominally the lowest speed at which an engine failure may simulated. The next speed ‘gate’ is 115 KIAS, known as Vxse, titled SEBAC, which is the Single Engine Best Angle of Climb. A handy speed to fly at when there are obstacles to clear and an engine has quit.
Next on the list Vyse at a mighty 121 KIAS is the SEBROC, great speed for going ‘up’ quickly if there are no obstacles ahead – distance 'to' - is not a problem.
Final gateway to nirvana – MEBROC; Multi Engine Best Rate of Climb, Vy 125 kIAS. Well done class. One last number to remember, normal cruise climb (comfortable angle) speed 160 KIAS.
Consider this; let’s call it a safe take off pathway, through ‘gates’; the first speed gate we must attend to is Vmca; pilots usually take a moment just before this speed to have a final look at the engine readouts. It is remarkably easy and very safe to ‘stop’ an aircraft of this ‘class’ in the 80 to 90 knot range if something is amiss; after this it becomes more difficult until it becomes unwise to attempt to stop at a higher speed (conditional). And so Gate 1 slides past all is well, now we need a ‘good’ speed to persuade the beast to leave the runway. Our friend Vx@100 seems to be a fair choice, so up we go, looking to accelerate to the lowest speed which will produce some climb performance; should an engine quit (airborne now runway gone). The easiest and quickest is Vxse 115, through that gate and the aircraft is now moving swiftly, the Vyse gate is behind in a heart beat and ‘cruise climb 160 KIAS is hot on its heels. Start to finish? What, perhaps 60 seconds. Stroll in the park. And so it is; until ‘something’ quits. To keep it simple, lets just lump the ‘quits’ compendium into one bucket and call it an engine failure.
Lets work backwards – say you are at 200 feet, 160 KIAS and climbing at 2000 feet per minute (FpM) and you go One Engine Inoperative (OEI); so what, it is an inconvenience and the paperwork is a nightmare; but you pedal it around and plonk it on the nearest suitable. Drinks all around.
Now, back to 200’. and you go OEI with 130 KIAS on the clock; problem. If you loose 5 knots, which is easy to do, you are back to a critical speed 125, provided you loose no more speed, then a performance climb to a safe height is possible. Should you go OEI at 125 KIAS the next safe speed is 121 for ‘climb performance’; it is terribly easy to loose those precious four or five knots; turbulence can rob you, slow reaction can rob you, incorrect technique can rob you of those precious few knots. But, if you go OEI below a single engine climb performance speed; you have a major problem.
The problem being that you need, indeed must, accelerate the aircraft to at least the lowest ‘climb’ speed. In order to achieve this, climbing must be put aside to avoid a further reduction in speed until the tombstone of Vmca appears on the clock. To accelerate at low level, OEI to a safe climb speed needs two essential elements; the most important of which is no obstacles at a greater height than you are. In short class, you need one essential element or the other to be available, preferably both, if you intend to get to the pub. Speed and height; Height and speed.
The King Air at Essendon had neither and failed to escape the clutches of the DFO.
There are serious questions to be answered related to the speed schedule; the aircraft was airborne with 116 KIAS ; only five knots shy of a performance climb speed and only one knot above the SEBAC speed. Why was there a progressive speed reduction to a terminal velocity of 108 KIAS instead of a level acceleration to a performance speed? Many ask why was the power not hauled off and the aircraft ‘dumped’ on the aerodrome. Sorry, far too many variables to say anything for sure.
To my Be20 qualified colleagues, I make my most sincere apologies for ‘brutalising’ and short hand handing the technicalities. “’twas a necessary evil M’luds”. MTF…..
Toot- toot.