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“SPEED, SPEED, SPEED” Warning
Anybody know why AB decided to call this warning by that name? Wouldn’t it have been more accurate to call it, “POWER, POWER, POWER” since it is a power (low energy) issue rather than a speed issue?
I think I have heard that warning maybe three times over the past seven years, one of which was when flying the transition to 5R at MMMX. The co-pilots response was to increase selected speed by 10 knots. Ofcourse that was the wrong response. Which got me thinking about the human factors aspect of AB naming this warning, “SPEED, SPEED, SPEED” when it is really a power issue. A little nit picking day for me here at home :) |
Get slow coming aboard the ship, the LSO will call, “POWER, POWER”; your idea has merit.
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For a non Airbus guy, can you guys say what causes this warning to come on?
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I think I have heard that warning maybe three times over the past seven years, one of which was when flying the transition to 5R at MMMX. No offence, but you must be doing something wrong, you'll hear that warning right before the protections kick in, so why are you pushing the aircraft that far, or allowing it to be pushed that far? Surely it's the sort of thing you'd only hear once in your life and then never again as you'd be scared to death by it? Or is it seen in some other way in your airline? Why would you be flying below VLS in normal operations? For a non Airbus guy, can you guys say what causes this warning to come on? |
Ok thanks, I figured it would be something like that, but thought it might also be something more complicated due to the OP's request.
If the warning is that the speed is too low, it seems perfectly reasonable to me that it says "SPEED" and not something else. The warning should be what is wrong, not what a supposed cure might be. In many airplanes, power by itself will only make the speed worse. |
B737. I used to teach datums and encourage guys to monitor N1% every so often on approach to anticipate changes when they had unwittingly set the wrong N1% for whatever configuration and manoeuvre was required.
On one occasion, on 3nm finals, I could see that the power set from F25 - F40 was going to cause the speed to decay PDQ. I waited and watched his eyes to see if they were alert. Nothing happened, so I called 'Power' which was where the error lay, but before the speed had decayed below Vref and followed the descending green arrow. His eyes were fixated outside, and without looking inside he reduced power. My follow up hand restored the correct setting and he landed. Afterwards he said that, without thinking, I had meant he had too much power. I reflected and wondered what would have been better. "Check power!" Proactive. wait for speed to decay, "Speed" (SOP) reactive. "increase power" proactive, but that could have caused a without thought agricultural handful. "Set 62%" proactive (non SOP.) "Power" was not an SOP call out, but that was the root cause of what was going to be an error that would have triggered an SOP call out. Being plots were are taught to be proactive. I thought I was being correct, but human nature defeated me. At least he learnt the lesson and took away the need to check more than the damned FD and looking outside. Energy management has various parameters under our control. |
Giggit...
The warning has nothing to do with airspeed. It independent of protections. It has nothing to do with VLS, this warning can trigger at any airspeed within its reporting envelope. The warning indicates thrust is limited. If flying AT off, increase thrust, if flying AT on, you must push the TL's past the climb detent. “A low energy warning alerts pilots when aircraft energy is insufficient to achieve a climbing flight path through pitch control alone. The “SPEED, SPEED, SPEED” voice alert repeats every 5 seconds while the condition exists. Thrust must be increased to achieve a climbing flight path. The low energy warning is computed by the FACs. It is available inconfigurations 2, 3, and FULL and is based on aircraft configuration, airspeed deceleration rate, and flight path angle.” |
Originally Posted by Vessbot
(Post 10059405)
For a non Airbus guy, can you guys say what causes this warning to come on?
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Originally Posted by CaptainMongo
(Post 10059371)
Anybody know why AB decided to call this warning by that name? Wouldn’t it have been more accurate to call it, “POWER, POWER, POWER” since it is a power (low energy) issue rather than a speed issue?
I think I have heard that warning maybe three times over the past seven years, one of which was when flying the transition to 5R at MMMX. The co-pilots response was to increase selected speed by 10 knots. Ofcourse that was the wrong response. Which got me thinking about the human factors aspect of AB naming this warning, “SPEED, SPEED, SPEED” when it is really a power issue. A little nit picking day for me here at home :) |
CaptainMongo speaks the truth.
Only heard it once, and on that occasion, the speed was still well clear of Vls. With a flat pitch attitude turning into the wind on base, our FPA steepened rapidly without a corresponding speed increase as we hit a leeside rotor. I.e. we lost energy, rather than traded it... The alert sounded before a pitch adjustment was made. ATHR was waking up, responded sufficiently. It is called the "low energy" alert for a reason. Its all in the FCOM DSC section, and worth a brief anywhere one might mention "terrain induced windshear" or similar. |
Originally Posted by Vessbot https://www.pprune.org/images/buttons/viewpost.gif For a non Airbus guy, can you guys say what causes this warning to come on? An aural low-energy “SPEED SPEED SPEED” alert, repeated every 5 s, warns the pilot that the aircraft’s energy level is going below a threshold under which he has to increase thrust, in order to regain a positive flight path angle through pitch control. It is available in Configuration 2, 3, and FULL. The FAC computes the energy level with the following inputs: ‐ Aircraft configuration ‐ Horizontal deceleration rate ‐ Flight path angle. The aural alert is inhibited when: ‐ TOGA is selected, or ‐ Below 100 ft RA, or ‐ Above 2 000 ft RA, or ‐ Alpha-floor, or the ground proximity warning system alert is triggered, or ‐ In alternate or direct law, or ‐ If both radio altimeters fail. During deceleration, the low-energy aural alert is triggered before alpha floor (unless alpha floor is triggered by stick deflection). The amount of time between the two alerts depends on the deceleration rate. en it’s up to you - to push it down or to increase power. Which is a lot to think of, if you're in that situation. So the solution is to select (pull) 160kts on downwind, to ensure that you have enough energy on base and final, rather than allow the aircraft to drift the speed back to the minimum (as it will do on managed (automatic) speed). |
Too Slow!
Shouldn't the call be, "TOO SLOW, TOO SLOW, TOO SLOW!
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Which got me thinking about the human factors aspect of AB naming this warning, “SPEED, SPEED, SPEED” when it is really a power issue. |
CaptainMongo
I know that technically it is independent of protections, but without reacting to it, the next thing you're probably going to see is Alpha Floor which means you've really cocked up. My reading says that "if the aircraft decelerates at 1 kt/sec, and: - The FPA is -3 ̊, the alert will trigger at approximately VLS -8, - The FPA is -4 ̊, the alert will trigger at approximately VLS -2.", therefore for practical purposes, the warning is based on speed. I appreciate that it may call SPEED SPEED at speeds higher than VLS, but I can't see why it should do that under normal operations. Either way, it also would seem odd that it would call out SPEED SPEED if it wasn't telling you to increase speed. Still doesn't explain how you've managed it 3 times in 7 years when getting in that position means you're manoeuvring with inappropriate speeds, or am I still missing something? I know it can occur when the FDs are not being followed, eg a situation where you're in THR IDLE/OP DES and you pitch above the FD bars (not flying in SPEED mode), not sure why you'd be doing that unless you were actively trying to have a chat with the boss? Otherwise, what are you doing turning near or below VLS? If as the others say, it's a result of windshear or rotor effects etc, you've selected an inappropriate speed for the turn in those conditions, you'd be foolish to be anywhere near VLS unless you're flying in a straight line even on a nice day. My airlines policy is not to fly below green dot whilst clean, S speed with flaps 1 and F speed/managed Vapp with all the goodies GS mini gives you, it keeps you safe for the all sensible reasons. I don't mean to appear obtuse, it just seems like a pretty odd thing to hear on a regular basis. |
At least he learnt the lesson and took away the need to check more than the damned FD and looking outside. Energy management has various parameters under our control With regard to the SOP calls in some airlines of "Speed" to caution the PF of undesired out of tolerance IAS indications. Some operators prefer a call of "Speed low" or Speed high." This at least gives the PF an indication of the direction of speed error. It also has the advantage of picking up an erroneous airspeed problem quickly, if one ASI disagrees with the others. Same principle with a call of "Altimeter." Better to say "Altimeter High" or "Altimeter Low." "Sink Rate" is yet another vague call. Usually said on final approach. "Sink Rate high" implies urgency which in the case of below 500 feet on short final is true |
Is simply brings your attention to the wayward parameter, BANK, PITCH, SPEED all direct your attention to the appropriate instrument. POWER POWER might make you look at the N1 or EPR gauges which won't help, if you look at the IAS then you will recognise the condition and should do something about it.
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"Sink Rate" is yet another vague call. Usually said on final approach. "Sink Rate high" implies urgency which in the case of below 500 feet on short final is true |
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).
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My airlines policy is not to fly below green dot whilst clean, S speed with flaps 1 and F speed/managed Vapp with all the goodies GS mini gives you, it keeps you safe for the all sensible reasons. Taking thrust levers out of CLB for more thrust has been stopped by Airbus. |
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. Good for 'lazy' autothrust / low energy situation, not so good below 100' :ouch:
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Doesn't the autothrust not reengage below 100' so you end up getting climb thrust and doing a fly by?
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Originally Posted by Checkboard
(Post 10059790)
An aural low-energy “SPEED SPEED SPEED” alert, repeated every 5 s, warns the pilot that the aircraft’s energy level is going below a threshold under which he has to increase thrust, in order to regain a positive flight path angle through pitch control.
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.
Originally Posted by _Phoenix
(Post 10059937)
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." |
Originally Posted by Checkboard
(Post 10060390)
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.
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Originally Posted by vilas
(Post 10059842)
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. |
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. |
What was the vertical mode, was the airplane pitching to maintain speed?
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CaptainMongo
Can you quote something from the FCOM on that, our manual specifically directs to advance thrust. |
tom775257
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. |
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 |
Mongo
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/ |
“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. |
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.
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Originally Posted by _Phoenix
(Post 10061181)
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. |
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Sorry, I'm not following. You'll have to be more specific with what you're replying to and how your facts bear on that.
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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) |
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. |
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.
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Airbus cadet pilots are transferring from 'Flying for Dummies' aeronautical college to MIT so they can understand WTF the a/c is talking about. :ugh:
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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.
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