B737 classic QUESTIONS AFTER RECURRENT TRAINING
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B737 QUESTIONS AFTER RECURRENT TRAINING
Hi all!
I've spent a few days on a recurrent training, and it's amazing as new questions always arise while talking to other people, even when you thought you knew something, maybe an instructor seems to be ABSOLUTELY convinced of what he's telling
So here's a short list of questions, some are interesting details, some are close to rubbish, but when some people seem to be so sure, you wonder if the earth is flat or round...
Let's see who can score more points!
1) Why the top of the yellow bar on the speed tape (the minimum maneuver speed ) is not coincident with the VREF and the green dot (flaps up maneuvering )?
Aren't they all supposed to be 1.3 VS??
2) On the ground you notice a difference of 7° degrees between the two IRS headings.
Can the airplane be dispatched?
3) Why is there a dead band on the elevators cables, and not on the ailerons cables?
4) Is it true the engine fire extinguisher does NOT reach the gearbox?
5) Once for all: is it necessary or not to put the Standby Power switch to BAT in order to REALLY check if the Inverter is capable of producing current?
6) Why in the Brake cooling Schedule table in the QRH the upper right data are missing?
I mean: is it not possible to abort at 140 knots at 60 tons at an elevation of 2000ft?
Yes, me thinks!
7) Why in the WINDOW HEAT OFF non normal cklist we don't have to pull the Windshiels air controls, while we do have to do it in the WINDOW OVERHEAT nncklist?
(The condition is the same, in both cases the windshields will not be heated).
8) If we lose the Battery Bus inflight, do the Pack valves remain open?
9) On airplanes that have a DCPCS, is it true there are THREE motors on the main outflow valve instead of two?
10) Discussing the ABORTED ENGINE START Recall Items, I've heard some people stating we do have to motor the engine after a shutdown due to NO OIL PRESSURE INDICATION by the time the engine is stabilized at idle!!!!
Can you believe that?
11) Is the radioaltimeter "directional"? I mean, does it read more if you are in a banked turn?
12) Is the dog going to FREEZE TO DEATH if they load it by mistake in the REAR cargo hold?
I'm absolutely convinced NOT, but someone is absolutely convinced YES, so it's a lot of fun, you know...
13) Is the ignition spark more intense in the FLT position?
I don't think so. It's just activated on both igniters.
Or...
LEM
I've spent a few days on a recurrent training, and it's amazing as new questions always arise while talking to other people, even when you thought you knew something, maybe an instructor seems to be ABSOLUTELY convinced of what he's telling
So here's a short list of questions, some are interesting details, some are close to rubbish, but when some people seem to be so sure, you wonder if the earth is flat or round...
Let's see who can score more points!
1) Why the top of the yellow bar on the speed tape (the minimum maneuver speed ) is not coincident with the VREF and the green dot (flaps up maneuvering )?
Aren't they all supposed to be 1.3 VS??
2) On the ground you notice a difference of 7° degrees between the two IRS headings.
Can the airplane be dispatched?
3) Why is there a dead band on the elevators cables, and not on the ailerons cables?
4) Is it true the engine fire extinguisher does NOT reach the gearbox?
5) Once for all: is it necessary or not to put the Standby Power switch to BAT in order to REALLY check if the Inverter is capable of producing current?
6) Why in the Brake cooling Schedule table in the QRH the upper right data are missing?
I mean: is it not possible to abort at 140 knots at 60 tons at an elevation of 2000ft?
Yes, me thinks!
7) Why in the WINDOW HEAT OFF non normal cklist we don't have to pull the Windshiels air controls, while we do have to do it in the WINDOW OVERHEAT nncklist?
(The condition is the same, in both cases the windshields will not be heated).
8) If we lose the Battery Bus inflight, do the Pack valves remain open?
9) On airplanes that have a DCPCS, is it true there are THREE motors on the main outflow valve instead of two?
10) Discussing the ABORTED ENGINE START Recall Items, I've heard some people stating we do have to motor the engine after a shutdown due to NO OIL PRESSURE INDICATION by the time the engine is stabilized at idle!!!!
Can you believe that?
11) Is the radioaltimeter "directional"? I mean, does it read more if you are in a banked turn?
12) Is the dog going to FREEZE TO DEATH if they load it by mistake in the REAR cargo hold?
I'm absolutely convinced NOT, but someone is absolutely convinced YES, so it's a lot of fun, you know...
13) Is the ignition spark more intense in the FLT position?
I don't think so. It's just activated on both igniters.
Or...
LEM
Last edited by LEM; 30th Nov 2005 at 02:56.
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LEM, an attempt at Questions 1 and 11, the others are about 6 aeroplane conversions in my past.
Vref is 1.3 Vs, Vls is 1.3 G (or 1.2 G in some jurisdictions)
No, it will read correct Radio Altitude, the emission is over quite a large non-directional area, and will provide you a Radio Altitude for the first pulses to be returned to the aircraft. (A severely banked turn MAY give the results that you suggest).
Regards,
Old Smokey
1) Why the top of the yellow bar on the speed tape (the minimum maneuver speed ) is not coincident with the VREF and the green dot (flaps up maneuvering )?
Is the radioaltimeter "directional"? I mean, does it read more if you are in a banked turn?
Regards,
Old Smokey
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aborted engine start
by doing the checklist, you may ruin a few bearings, but if you don't motor the engine and get the heat and fire out of there, you may melt quite a few blades and other components, not to mention the possible need to use the fire bottle soon thereafter.
more later, if i can remember those things
regarding your number 5-
how else would you check it, unless you came to a dark aircraft and started the APU etc?
if you come to the gate and it has ground power, and then start the APU whilst still with ground power, i think you will only have a few milli seconds between the switch over from ground power to APU power to check if the standby bus is working otherwise.
and then again, the old rule that never dies, you do what the man/woman with the ink pen and your checkride form says!
more later, if i can remember those things
regarding your number 5-
how else would you check it, unless you came to a dark aircraft and started the APU etc?
if you come to the gate and it has ground power, and then start the APU whilst still with ground power, i think you will only have a few milli seconds between the switch over from ground power to APU power to check if the standby bus is working otherwise.
and then again, the old rule that never dies, you do what the man/woman with the ink pen and your checkride form says!
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Dog won't freeze ,the aft cargo hold is heated by air from the passanger cabin.It's not so warm as fwd cargo hold,which is heated directly by airflow from electronics..
13. in flt ,both igniters activated.The spark is the same,as far as I know.
2 From the DDPG the airplane can be dispatched under some conditions (day VMC,...) with only one IRS operative.
But ,I guess your question about difference between headings fits somewhere else.
7 Maybe it's night and I'm tired ,but Lem,where is the window heat off NNC?
4 The gearbox is placed on the 'outside' of the engine ,that's the reason for the particular shape of the 737 nacelle,and indeed the fire extinguisher does not reach the gearbox.
13. in flt ,both igniters activated.The spark is the same,as far as I know.
2 From the DDPG the airplane can be dispatched under some conditions (day VMC,...) with only one IRS operative.
But ,I guess your question about difference between headings fits somewhere else.
7 Maybe it's night and I'm tired ,but Lem,where is the window heat off NNC?
4 The gearbox is placed on the 'outside' of the engine ,that's the reason for the particular shape of the 737 nacelle,and indeed the fire extinguisher does not reach the gearbox.
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Regarding point 9), yes its true you have 3 DC motors at the outflow valve, one for each automatic controller (they're interchangeable) and a different one for manual mode.
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4) Is it true the engine fire extinguisher does NOT reach the gearbox?
why should it?
7) Why in the WINDOW HEAT OFF non normal cklist we don't have to pull the Windshiels air controls, while we do have to do it in the WINDOW OVERHEAT nncklist?
(The condition is the same, in both cases the windshields will not be heated).
g00d question. i dunno.
11) Is the radioaltimeter "directional"? I mean, does it read more if you are in a banked turn?
i -think- its built in fixed to the z-axis of the plane near the MLG.
12) Is the dog going to FREEZE TO DEATH if they load it by mistake in the REAR cargo hold?
I'm absolutely convinced NOT, but someone is absolutely convinced YES, so it's a lot of fun, you know...
just put a bottle of water in a bag an see if it freezes - no, it doesn't.
13) Is the ignition spark more intense in the FLT position?
I don't think so. It's just activated on both igniters.
Or...
well, both spark plugs are now working instead of only one when in CONT
why should it?
7) Why in the WINDOW HEAT OFF non normal cklist we don't have to pull the Windshiels air controls, while we do have to do it in the WINDOW OVERHEAT nncklist?
(The condition is the same, in both cases the windshields will not be heated).
g00d question. i dunno.
11) Is the radioaltimeter "directional"? I mean, does it read more if you are in a banked turn?
i -think- its built in fixed to the z-axis of the plane near the MLG.
12) Is the dog going to FREEZE TO DEATH if they load it by mistake in the REAR cargo hold?
I'm absolutely convinced NOT, but someone is absolutely convinced YES, so it's a lot of fun, you know...
just put a bottle of water in a bag an see if it freezes - no, it doesn't.
13) Is the ignition spark more intense in the FLT position?
I don't think so. It's just activated on both igniters.
Or...
well, both spark plugs are now working instead of only one when in CONT
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With the engine that I currently operate (RR Trent), the recommendation following aborted start due to no oil pressure is to still carry out a motoring cycle.
This is taken from another thread, but applies to point 10) here.
Could you elaborate a bit?
I still find it hard to conceive such a procedure...
Thanks LEM
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Hi LEM,
The old thinking was that engine start was aborted if there was no oil pressure indication by light up. That part of the procedure still remains.
Previous thinking was to never operate an engine in ANY manner without oil pressure (one that I happily accepted). Current thinking is that the 'blow out' cycle is important, and, with roller bearings, little damage is likely to arise at the very low RPM. Allied with this, the torque supplied by the starter motor would in all likelyhood be insufficient to overcome excessive friction in an 'oilless environment', and would therefore be self regulating in protecting significant damage.
Personally, I don't like it too much, but there you go.
Regards,
Old Smokey
The old thinking was that engine start was aborted if there was no oil pressure indication by light up. That part of the procedure still remains.
Previous thinking was to never operate an engine in ANY manner without oil pressure (one that I happily accepted). Current thinking is that the 'blow out' cycle is important, and, with roller bearings, little damage is likely to arise at the very low RPM. Allied with this, the torque supplied by the starter motor would in all likelyhood be insufficient to overcome excessive friction in an 'oilless environment', and would therefore be self regulating in protecting significant damage.
Personally, I don't like it too much, but there you go.
Regards,
Old Smokey
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About the dog...
A captain in our airline tried it once on a flight to PMI... the dog came out severely undercooled and they had to put him to "eternal sleep"... So it is NOT heated enough to put any AVI in there. The heat from the pax. cabin is simply insufficient.
The forward cargo bay is the only one to put any live animals in.
Greetz,
Despegue
A captain in our airline tried it once on a flight to PMI... the dog came out severely undercooled and they had to put him to "eternal sleep"... So it is NOT heated enough to put any AVI in there. The heat from the pax. cabin is simply insufficient.
The forward cargo bay is the only one to put any live animals in.
Greetz,
Despegue
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A captain in our airline tried it once on a flight to PMI... the dog came out severely undercooled and they had to put him to "eternal sleep"... So it is NOT heated enough to put any AVI in there. The heat from the pax. cabin is simply insufficient.
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Regarding the rear cargo hold, my assumption is quite simple: if the temperature was to fall below zero celsius, the passengers would collect frozen baggage at the end of the flight.
Imagine all the liquids in beauty cases and stuff like that...
But sure the chicks need a warmer welcome to this world in order to survive
Imagine all the liquids in beauty cases and stuff like that...
But sure the chicks need a warmer welcome to this world in order to survive
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RadAlts give a reasonable indication of height during normal banked turn where the straight line distance along the "normal axis" from the plane to ground is greatly increased. Therfore, they are not directional.
LEM, great questions, sorry I was late into the thread.
Q1) Why the top of the yellow bar on the speed tape (the minimum maneuver speed ) is not coincident with the VREF and the green dot (flaps up maneuvering )?
Aren't they all supposed to be 1.3 VS??
A1) No, they are two different things. With flaps retracted, yellow bar indicates 0.3g manoeuvre margin. Green dot indicates flaps up manoeuvring speed based upon actual weight (ie stall speed) rather than standard block speed (eg 210kts).
Q2) On the ground you notice a difference of 7° degrees between the two IRS headings.
Can the airplane be dispatched?
A2) One IRS will be in error (unless both are 3.5 degrees out!), find out which one and if you can’t get it fixed, switch it off and you may be able to despatch with the serviceable one. See MEL for details on this.
Q3) Why is there a dead band on the elevators cables, and not on the ailerons cables?
A3) I am fairly sure that is because of the manual reversion mode where the elevator PCU (without power) is used as a link to the elevator tab rods. The dead band is always about 1.5 inches during manual reversion because of this, so I think it is this slack not being fully taken up when the PCU is powered.
Q4) Is it true the engine fire extinguisher does NOT reach the gearbox?
A4) Yes
Q5) Once for all: is it necessary or not to put the Standby Power switch to BAT in order to REALLY check if the Inverter is capable of producing current?
A5) I think so, unless anybody knows another way.
Q6) Why in the Brake cooling Schedule table in the QRH the upper right data are missing?
I mean: is it not possible to abort at 140 knots at 60 tons at an elevation of 2000ft?
Yes, me thinks!
A7) Yes it is possible to abort at those conditions – and faster, heavier & higher. The reference brake energy in the missing upper right area is probably not quantifiable thus we have to assume the worst nearest case ie approx 30 million foot pounds in my 22K -300 QRH. As it was an RTO it is not factored for head/tailwind so this puts you firmly into the fuse plug melt zone on the brake cooling schedule page.
Q7) Why in the WINDOW HEAT OFF non normal cklist we don't have to pull the Windshiels air controls, while we do have to do it in the WINDOW OVERHEAT nncklist?
(The condition is the same, in both cases the windshields will not be heated).
A7) I don’t have a WINDOW HEAT OFF nnc, but perhaps the reason is that heat has been removed due to the window being up to temperature rather than a full overheat. Like what you get sitting on a hot apron in full sun when a green ON light extinguishes.
Q8) If we lose the Battery Bus inflight, do the Pack valves remain open?
A8) Don’t know, sounds like one for the next time you are in the simulator.
Q9) On airplanes that have a DCPCS, is it true there are THREE motors on the main outflow valve instead of two?
A9) Yes, one for each auto controller and one for manual controller.
Q10) Discussing the ABORTED ENGINE START Recall Items, I've heard some people stating we do have to motor the engine after a shutdown due to NO OIL PRESSURE INDICATION by the time the engine is stabilized at idle!!!!
Can you believe that?
A10) Yes I can, because it is what the QRH says that you must do, therefore we must do it. We cannot start inventing our own procedures because we think we know better. The manufacturers know more than us and have for a host of reasons come up with the QRH. We are on very thin ice if we go against it.
Q11) Is the radioaltimeter "directional"? I mean, does it read more if you are in a banked turn?
A11) Yes because the LRRA beams are directional – vertically down the z axis from the transmitter aerials. However the over-indication in a banked turn would be insignificant until the AoB was beyond 30 degrees (Cosine of 30 is 0.866). And you really should not be beyond 30 degrees AoB when below 2500ft RA.
Q12) Is the dog going to FREEZE TO DEATH if they load it by mistake in the REAR cargo hold?
A12) On a long flight possibly yes. There is some heating to the aft hold as the cabin air is circulated around it, but the front has extra heating from the E & E bay and should be used for AVI.
Q13) Is the ignition spark more intense in the FLT position?
A13) No, same intensity but both igniters are used.
Q1) Why the top of the yellow bar on the speed tape (the minimum maneuver speed ) is not coincident with the VREF and the green dot (flaps up maneuvering )?
Aren't they all supposed to be 1.3 VS??
A1) No, they are two different things. With flaps retracted, yellow bar indicates 0.3g manoeuvre margin. Green dot indicates flaps up manoeuvring speed based upon actual weight (ie stall speed) rather than standard block speed (eg 210kts).
Q2) On the ground you notice a difference of 7° degrees between the two IRS headings.
Can the airplane be dispatched?
A2) One IRS will be in error (unless both are 3.5 degrees out!), find out which one and if you can’t get it fixed, switch it off and you may be able to despatch with the serviceable one. See MEL for details on this.
Q3) Why is there a dead band on the elevators cables, and not on the ailerons cables?
A3) I am fairly sure that is because of the manual reversion mode where the elevator PCU (without power) is used as a link to the elevator tab rods. The dead band is always about 1.5 inches during manual reversion because of this, so I think it is this slack not being fully taken up when the PCU is powered.
Q4) Is it true the engine fire extinguisher does NOT reach the gearbox?
A4) Yes
Q5) Once for all: is it necessary or not to put the Standby Power switch to BAT in order to REALLY check if the Inverter is capable of producing current?
A5) I think so, unless anybody knows another way.
Q6) Why in the Brake cooling Schedule table in the QRH the upper right data are missing?
I mean: is it not possible to abort at 140 knots at 60 tons at an elevation of 2000ft?
Yes, me thinks!
A7) Yes it is possible to abort at those conditions – and faster, heavier & higher. The reference brake energy in the missing upper right area is probably not quantifiable thus we have to assume the worst nearest case ie approx 30 million foot pounds in my 22K -300 QRH. As it was an RTO it is not factored for head/tailwind so this puts you firmly into the fuse plug melt zone on the brake cooling schedule page.
Q7) Why in the WINDOW HEAT OFF non normal cklist we don't have to pull the Windshiels air controls, while we do have to do it in the WINDOW OVERHEAT nncklist?
(The condition is the same, in both cases the windshields will not be heated).
A7) I don’t have a WINDOW HEAT OFF nnc, but perhaps the reason is that heat has been removed due to the window being up to temperature rather than a full overheat. Like what you get sitting on a hot apron in full sun when a green ON light extinguishes.
Q8) If we lose the Battery Bus inflight, do the Pack valves remain open?
A8) Don’t know, sounds like one for the next time you are in the simulator.
Q9) On airplanes that have a DCPCS, is it true there are THREE motors on the main outflow valve instead of two?
A9) Yes, one for each auto controller and one for manual controller.
Q10) Discussing the ABORTED ENGINE START Recall Items, I've heard some people stating we do have to motor the engine after a shutdown due to NO OIL PRESSURE INDICATION by the time the engine is stabilized at idle!!!!
Can you believe that?
A10) Yes I can, because it is what the QRH says that you must do, therefore we must do it. We cannot start inventing our own procedures because we think we know better. The manufacturers know more than us and have for a host of reasons come up with the QRH. We are on very thin ice if we go against it.
Q11) Is the radioaltimeter "directional"? I mean, does it read more if you are in a banked turn?
A11) Yes because the LRRA beams are directional – vertically down the z axis from the transmitter aerials. However the over-indication in a banked turn would be insignificant until the AoB was beyond 30 degrees (Cosine of 30 is 0.866). And you really should not be beyond 30 degrees AoB when below 2500ft RA.
Q12) Is the dog going to FREEZE TO DEATH if they load it by mistake in the REAR cargo hold?
A12) On a long flight possibly yes. There is some heating to the aft hold as the cabin air is circulated around it, but the front has extra heating from the E & E bay and should be used for AVI.
Q13) Is the ignition spark more intense in the FLT position?
A13) No, same intensity but both igniters are used.
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Thanks for all the replies!
I still have some doubts:
2) What I meant was if there is some sort of official tolerance in indicating the heading.
The comparator will warn us for a difference in pitch or roll, but not for a difference in heading.
I tried to find out in the maintenance manual, but couldn't find until what difference in degrees is the IRS heading considered acceptable.
Of course for large deviations there is no problem, as one IRS will be obviously wrong thus US, but the doubt arises for small deviations, like 3° ....
5) So what voltage do we see when at the gate, ground power or APU on, we select INV on the Ac Meter Selector?
7) On some airplanes there are no green ON lights for the windshields (making it closer to a dark cockpit), but there are OFF amber lights.
The cecklist is WINDOW HEAT OFF, NNC.3.2., and it says:
Condition: A window heat OFF light illuminated indicates that the controller may have removed all heat to a window due to an excessive temperature.
WINDOW HEAT SWITCH..........................................OFF
Limit airspeed to 250 knots maximum below 10,000 feet.
Probably they forgot to address the subsequent fogging consequences as they did in the WINDOW OVERHEAT NNC.
10) You are right, the manufacturer made the cecklist like that.
It still seems at first sight a nonsense to motor the engine if we want to protect the bearings, but maybe the advantages of cooling the core after the starting EGT peak is greater than the quasi-null stress on the bearings at such low speed.
So I swear from now on I'll make a motoring in this case also!
12) Regarding the dog... actually my question was too simplistic: it really depends...
Are they loading a SaintBernard or a Chihuaua?
Is it a one hour or a four hours flight?
Is the passengers compartment full or almost empty?
I'll try to put a bottle of water next time I fly to Sharm, but at present we only fly short range...
Probably a little dog might not survive, but I still think the story of finding it hard-frozen is an urban myth.
Thank you all!
LEM
I still have some doubts:
2) What I meant was if there is some sort of official tolerance in indicating the heading.
The comparator will warn us for a difference in pitch or roll, but not for a difference in heading.
I tried to find out in the maintenance manual, but couldn't find until what difference in degrees is the IRS heading considered acceptable.
Of course for large deviations there is no problem, as one IRS will be obviously wrong thus US, but the doubt arises for small deviations, like 3° ....
5) So what voltage do we see when at the gate, ground power or APU on, we select INV on the Ac Meter Selector?
7) On some airplanes there are no green ON lights for the windshields (making it closer to a dark cockpit), but there are OFF amber lights.
The cecklist is WINDOW HEAT OFF, NNC.3.2., and it says:
Condition: A window heat OFF light illuminated indicates that the controller may have removed all heat to a window due to an excessive temperature.
WINDOW HEAT SWITCH..........................................OFF
Limit airspeed to 250 knots maximum below 10,000 feet.
Probably they forgot to address the subsequent fogging consequences as they did in the WINDOW OVERHEAT NNC.
10) You are right, the manufacturer made the cecklist like that.
It still seems at first sight a nonsense to motor the engine if we want to protect the bearings, but maybe the advantages of cooling the core after the starting EGT peak is greater than the quasi-null stress on the bearings at such low speed.
So I swear from now on I'll make a motoring in this case also!
12) Regarding the dog... actually my question was too simplistic: it really depends...
Are they loading a SaintBernard or a Chihuaua?
Is it a one hour or a four hours flight?
Is the passengers compartment full or almost empty?
I'll try to put a bottle of water next time I fly to Sharm, but at present we only fly short range...
Probably a little dog might not survive, but I still think the story of finding it hard-frozen is an urban myth.
Thank you all!
LEM
Further to Q12) “Is the dog going to FREEZE TO DEATH if they load it by mistake in the REAR cargo hold?”
I found this in Boeing publication D6-76300-32, Detail Specification for a 737-300
Air Conditioning
21-27-00 CARGO AIR DISTRIBUTION
21-27-10 Forward Cargo Compartment
Forward cargo compartment stabilised air temperature shall be maintained above 40 degrees F everywhere at a distance more than 8 inches from the exterior walls and floor in flight up to maximum certified altitude. The cargo door area shall be excluded from this requirement.
21-27-20 Aft Cargo Compartment
Aft cargo compartment temperature shall be maintained above freezing (32 degrees F) when measured at least 8 inches from its exterior walls and floor. The door area shall be excluded from this requirement.
I found this in Boeing publication D6-76300-32, Detail Specification for a 737-300
Air Conditioning
21-27-00 CARGO AIR DISTRIBUTION
21-27-10 Forward Cargo Compartment
Forward cargo compartment stabilised air temperature shall be maintained above 40 degrees F everywhere at a distance more than 8 inches from the exterior walls and floor in flight up to maximum certified altitude. The cargo door area shall be excluded from this requirement.
21-27-20 Aft Cargo Compartment
Aft cargo compartment temperature shall be maintained above freezing (32 degrees F) when measured at least 8 inches from its exterior walls and floor. The door area shall be excluded from this requirement.
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tried to find out in the maintenance manual, but couldn't find until what difference in degrees is the IRS heading considered acceptable.
beautiful
Also waiting for some official answers, anyway I have never experienced Hdg differences greater than a couple of degrees... so maybe if they become greater there is a problem somewhere. No one wrote an "Instruments cross-check for dummies" yet ? 
Request advice on this question: Departing very light weight on long runway (737) and perhaps for monitoring requirements, full thrust is used. The BRW is many tonnes less than even at the maximum assumed temp (say 55C).
Old Boeing manuals state that you should use V speeds for actual weight. On the other hand one performance engineer told me that is not so - that you use the V speeds for the actual OAT - even though they may be 20 knots or more higher than those for the actual weight. Seems a bit silly to me.
Why force the aircraft to stay on the runway longer than necessary. Also more chance of greater tyre wear and tear coupled with marginally greater risk of tyre failure at higher speeds?
Old Boeing manuals state that you should use V speeds for actual weight. On the other hand one performance engineer told me that is not so - that you use the V speeds for the actual OAT - even though they may be 20 knots or more higher than those for the actual weight. Seems a bit silly to me.
Why force the aircraft to stay on the runway longer than necessary. Also more chance of greater tyre wear and tear coupled with marginally greater risk of tyre failure at higher speeds?