“SPEED, SPEED, SPEED” Warning
Join Date: Sep 2016
Location: USA
Posts: 803
Likes: 0
Received 0 Likes
on
0 Posts
As most of us agree, the warning should point to the paramater in error. But despite your quote and others' elucidations, many still seem to point to the airspeed as the errant parameter, while from my understanding the speed can be perfectly normal and you can still get the warning.
By definition Speed, speed, speed is a warning about the low state of energy, about decaying of the kinetic energy, which is 1/2*m*speed^2. The flight instructor would warn the student in the same way about dangerously low speed condition, thenafter the student realizes that he has to add more power or to relax the pitch up (in a tight turn for instance).
On a serious note, a big pet peeve of mine about this topic is when people call it a "high altitude, low energy" situation. It is not low energy, from 30,000 feet you have gobs of energy below you (namely, 1491 knots' worth) to use. That is, as long as you have the understanding and fortitude to use it.
Of course, I know they mean "low kinetic energy" and not "low total energy," but in that case they could have just said "low airspeed" with no loss of information. But no, they have to muddy the waters by using the fancy high tech sounding term. Unqualified "energy" is supposed to mean "total energy."
If you are at F speed and make a 90º turn onto final then a very small overbank will have you into the "SPEED SPEED" regime. The aircraft isn't smart enough to look ahead at the flight path and see that you will be manoeuvring - that's what pilots are for. Blind reliance on the managed speed "keeping you safe" gets pilots into trouble. I would imagine that the poster who has seen this "three times in seven years" was also relying totally on managed speed.
Thread Starter
Join Date: Oct 2015
Location: 43N
Posts: 264
Likes: 0
Received 0 Likes
on
0 Posts
My guess is it can be seen it's a warning for approach and landing configurations. Airbus design philosophy is to use available automation. So with ATHR available it's not a thrust issue as thrust would already be at CLB. So it is change of flight path to get the correct speed. Taking thrust levers out of CLB for more thrust has been stopped by Airbus.
Can you quote something from the FCOM on that, our manual specifically directs to advance thrust.
Thread Starter
Join Date: Oct 2015
Location: 43N
Posts: 264
Likes: 0
Received 0 Likes
on
0 Posts
As Vessbot stated well, it is total energy state, I have been at 45,000’, pointed straight up, with 0 airspeed in an F-16, the least of my worries at that time was the airspeed my aircraft.
Three speed warnings. Two which I believed to be either spurious or extraordinarily conservative (that statement will certainly aggravate some, but after 36 years of flying, I believe I have a pretty good understanding of the energy state of my aircraft - I have not and would never maneuver a commercial aircraft aggressively)
All that said, the time I believed the warning which was valid was what I described and my FO’s instinctive reaction to it, which was inappropriate. His response was to add 10 knots to the SEL speed, because the airplane announced, “Speed, speed, speed.”. The warning is based on the current energy state and the FAC’s expected energy state of the aircraft. His reaction was incorrect.
Airbus designed this to focus the pilots attention on the energy state of the aircraft, yet the callout was speed thus my OP.
Three speed warnings. Two which I believed to be either spurious or extraordinarily conservative (that statement will certainly aggravate some, but after 36 years of flying, I believe I have a pretty good understanding of the energy state of my aircraft - I have not and would never maneuver a commercial aircraft aggressively)
All that said, the time I believed the warning which was valid was what I described and my FO’s instinctive reaction to it, which was inappropriate. His response was to add 10 knots to the SEL speed, because the airplane announced, “Speed, speed, speed.”. The warning is based on the current energy state and the FAC’s expected energy state of the aircraft. His reaction was incorrect.
Airbus designed this to focus the pilots attention on the energy state of the aircraft, yet the callout was speed thus my OP.
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,407
Likes: 0
Received 0 Likes
on
0 Posts
CaptainMongo
This was in FCOM Bulletins but these days either they have disappeared or are impossible to find. Let me try another time.
Can you quote something from the FCOM on that, our manual specifically directs to advance thrust.
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,407
Likes: 0
Received 0 Likes
on
0 Posts
tom775257
Yes! That's what I remember it was for approach. But it seems to have disappeared. What you find in FCTM is in connection with adverse weather.
I suspect Vilas is referring to phase advance which used to be allowed, moving the thrust levers above the climb gate for a short period of time to temporarily get man thrust / MCT until you click it back into climb when Athr will reengage.
WARNING THE FLIGHT CREW
The "SPEED, SPEED, SPEED" low energy warning (if available) is based on the aircraft speed, acceleration and flight path angle. This warning attracts the PF eyes to the speed scale, and request rapid thrust adjustment. In windshear conditions, it is the first warning to appear, before the activation of the alpha floor.
The "SPEED, SPEED, SPEED" low energy warning (if available) is based on the aircraft speed, acceleration and flight path angle. This warning attracts the PF eyes to the speed scale, and request rapid thrust adjustment. In windshear conditions, it is the first warning to appear, before the activation of the alpha floor.
Join Date: Jan 2015
Location: Near St Lawrence River
Age: 53
Posts: 198
Likes: 0
Received 0 Likes
on
0 Posts
Of course, I know they mean "low kinetic energy" and not "low total energy," but in that case they could have just said "low airspeed" with no loss of information. But no, they have to muddy the waters by using the fancy high tech sounding term. Unqualified "energy" is supposed to mean "total energy
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,407
Likes: 0
Received 0 Likes
on
0 Posts
Mongo
Phew! Finally I got it. It's very long one.
Phew! Finally I got it. It's very long one.
REASON FOR ISSUE
During the approach, with the A/THR active, Airbus recommended to set the thrust levers above the CL detent (but below the MCT detent), in exceptional circumstances, if the speed significantly dropped below VAPP. However this procedure is not trained and proved to have more drawbacks than advantages. Therefore, Airbus no longer recommends to use this procedure. The procedure is deleted from the operational documentation.
If the A/THR performance is not satisfactory, the flight crew should take over, and control the thrust manually.
GENERAL
The purpose of this FCOM Bulletin is to highlight certain aspects of aircraft handling during final approach, and to illustrate that the feedback received from in-service experience merits further attention. Although approach in turbulence is part of this discussion, windshear in approach is not addressed
here. For more details on the subjects of "Windshear in Approach" and "Operations in Windshear or Downburst Conditions", Refer to PRO-SUP-91-20.
APPROACH STABILIZATION CRITERIA
The prerequisite for a successful final approach and landing is to stabilize the aircraft on the final approach trajectory in pitch, thrust, airspeed, and bank angle. This signifies that the:
‐ Aircraft is established on the:
• Final approach trajectory, and only minor heading corrections are necessary (except for indirect or curve approaches) to correct the effect of external conditions, acting on the roll axis
• Final approach vertical flight path, and only minor pitch corrections are necessary to correct the effect of external conditions;
‐ The target speed is maintained on the desired descent path, with the appropriate thrust (not stabilized at idle).
Airbus policy requires that stabilized conditions be reached at 1 000 ft Height Above Threshold in IMC, and 500 ft feet in VMC, and that they be kept down to the flare height.
In turbulent conditions, there may be heading, pitch, and thrust corrections of such a magnitude that it could be difficult to determine when to consider the approach stabilization criteria as being lost. Thrust corrections, in particular with the A/THR ON, could lead engines to temporarily reduce thrust to idle, which may not be desirable close to the ground, if the aircraft level of energy is low.
A318/A319/A320/A321 FLIGHT CREW
OPERATING MANUAL
FLIGHT CREW BULLETINS
AIRCRAFT HANDLING IN FINAL APPROACH
AXM A318/
During the approach, with the A/THR active, Airbus recommended to set the thrust levers above the CL detent (but below the MCT detent), in exceptional circumstances, if the speed significantly dropped below VAPP. However this procedure is not trained and proved to have more drawbacks than advantages. Therefore, Airbus no longer recommends to use this procedure. The procedure is deleted from the operational documentation.
If the A/THR performance is not satisfactory, the flight crew should take over, and control the thrust manually.
GENERAL
The purpose of this FCOM Bulletin is to highlight certain aspects of aircraft handling during final approach, and to illustrate that the feedback received from in-service experience merits further attention. Although approach in turbulence is part of this discussion, windshear in approach is not addressed
here. For more details on the subjects of "Windshear in Approach" and "Operations in Windshear or Downburst Conditions", Refer to PRO-SUP-91-20.
APPROACH STABILIZATION CRITERIA
The prerequisite for a successful final approach and landing is to stabilize the aircraft on the final approach trajectory in pitch, thrust, airspeed, and bank angle. This signifies that the:
‐ Aircraft is established on the:
• Final approach trajectory, and only minor heading corrections are necessary (except for indirect or curve approaches) to correct the effect of external conditions, acting on the roll axis
• Final approach vertical flight path, and only minor pitch corrections are necessary to correct the effect of external conditions;
‐ The target speed is maintained on the desired descent path, with the appropriate thrust (not stabilized at idle).
Airbus policy requires that stabilized conditions be reached at 1 000 ft Height Above Threshold in IMC, and 500 ft feet in VMC, and that they be kept down to the flare height.
In turbulent conditions, there may be heading, pitch, and thrust corrections of such a magnitude that it could be difficult to determine when to consider the approach stabilization criteria as being lost. Thrust corrections, in particular with the A/THR ON, could lead engines to temporarily reduce thrust to idle, which may not be desirable close to the ground, if the aircraft level of energy is low.
A318/A319/A320/A321 FLIGHT CREW
OPERATING MANUAL
FLIGHT CREW BULLETINS
AIRCRAFT HANDLING IN FINAL APPROACH
AXM A318/
Last edited by vilas; 26th Feb 2018 at 03:12.
Join Date: Jun 2000
Location: last time I looked I was still here.
Posts: 4,507
Likes: 0
Received 0 Likes
on
0 Posts
“Speed, speed, speed.”. The warning is based on the current energy state and the FAC’s expected energy state of the aircraft. His reaction was incorrect.
Airbus designed this to focus the pilots attention on the energy state of the aircraft, yet the callout was speed thus my OP.
Could it be that Airbus have tried to be overly smart and over simplify the a/c so that dummies can fly it,, but then they are caught out by the unexpected thinking pilot.
Airbus designed this to focus the pilots attention on the energy state of the aircraft, yet the callout was speed thus my OP.
Could it be that Airbus have tried to be overly smart and over simplify the a/c so that dummies can fly it,, but then they are caught out by the unexpected thinking pilot.
Join Date: Jul 2006
Location: Somewhere over the rainbow
Posts: 946
Likes: 0
Received 0 Likes
on
0 Posts
I heard that warning only once when my batch mate was doing his base flight and pitch up a bit too violently to lower the ROD during base leg and thus triggered the warning. From what I understand , in that case the warning can be stopped by either lowering the nose to recover a positive flight path angle and most likely an increase in airspeed or adding power which will also increase the speed. I don't see any situation where increasing the speed won't solve the problem. Therefore the Auto Call Out " Speed Speed Speed" does make sense to me.
Join Date: Sep 2016
Location: USA
Posts: 803
Likes: 0
Received 0 Likes
on
0 Posts
Actually they are correct, the total energy decreases under the work of the increased drag, since the initial total energy+work of drag force(-)=final total energy(lower). They say you have to increase Power(thrust force) to recover the lost of kinetic energy(and to recover the initial total energy) in order to keep the flight path. Otherwise, by keeping the lower total energy state you have to trade your potential energy towards the kinetic energy, before the alfa floor kicks in.
In the high altitude example I posted, that leads them to mistakenly infer "low energy" from "low speed" and forget about all the potential energy below them.
The example that this thread is based on is someone inferring "low speed" from the warning that's about low energy (but you can't really blame him, since the plane said "SPEED!") and increasing the speed (presumably via pitching down; CaptainMongo didn't clarify but that's what I'm inferring) which only worsened the total energy loss.
Last edited by Vessbot; 23rd Feb 2018 at 02:34.
Join Date: Jan 2015
Location: Near St Lawrence River
Age: 53
Posts: 198
Likes: 0
Received 0 Likes
on
0 Posts
It is about the conservation of the mechanical energy. The state of energy of a system can increase by receiving work = Force*distance or it can decrease by dissipating energy through friction (converted in thermal energy). In imagine at point A the total energy is U1 = beer_mass*g*h since vA = 0 . The the beer is accelerated by the total force (Fapp-Friction), that produces work (Fapp-Friction)*dAB. At point B the energy = U1 + K2 , where K2 = 0.5*beer_mass*vB^2. At point B the Fapp becomes =0 and only the Friction force change the energy state from K2 +U1 (at point B) to U1 at point C. The friction work=Friction*dBC = -K2.
Same logic at point C' the energy U2 = U1 + beer_mass*g*delta_h and the travel is shorter, part of the kinetic energy is changed into potential energy (the work of the gravity component acting on the same direction as the Friction force)
Same logic at point C' the energy U2 = U1 + beer_mass*g*delta_h and the travel is shorter, part of the kinetic energy is changed into potential energy (the work of the gravity component acting on the same direction as the Friction force)
Join Date: Sep 2016
Location: USA
Posts: 803
Likes: 0
Received 0 Likes
on
0 Posts
U is potential energy, not total. It's defined right there in the, um, definitions. Total is K+U. That's making the rest of your math jumbled. Also things with subscript 2 correspond with position C, not B. Also there are two separate scenarios; the first on the flat plane where potential energy stays the same, and the second up the incline where potential energy increases.
All that aside, you still didn't say what part of my post that bears on, or how it bears on it.
All that aside, you still didn't say what part of my post that bears on, or how it bears on it.
Join Date: Jan 2015
Location: Near St Lawrence River
Age: 53
Posts: 198
Likes: 0
Received 0 Likes
on
0 Posts
K=0 for v=0, I stated above for the feeling that I have to make it clear. There are two equations for energy conservation with K1=K3=0. Sorry, that's all, I'm at work, otherwise I would open a beer and listen to this hit: Echame La Culpa.
Join Date: Jun 2000
Location: last time I looked I was still here.
Posts: 4,507
Likes: 0
Received 0 Likes
on
0 Posts
Airbus cadet pilots are transferring from 'Flying for Dummies' aeronautical college to MIT so they can understand WTF the a/c is talking about.
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,407
Likes: 0
Received 0 Likes
on
0 Posts
It's a simple warning in approach about falling speed. Some thing like verbal trend arrow. Apart from WS the reason is flight path or thrust if in manual thrust. The practice of moving the thrust levers out of CLB towards MCT if taken too far has the potential(actually I am sure it has happened) of triggering GA mode which will effectively end the approach. So through the FC Bulletin which I mentioned it was stopped and complete switching to manual thrust was recommended. Either the the earlier or the later recommendation doesn't seem to exist in Airbus new manuals. So if a company manual has it then it will be a good idea to get Airbus position on the matter under tech request.