Define Vfe
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Also remember that the Vfe was first calculated when the A/C was test flown & most likely prior to that via the 'confuzer' & is really a structual limiting speed. I'd bet my right one (this time) that ALL A/C world over has exceeded the Vfe, the Vle & all the other V's at some stage during it's life maybe not by you but by somebody mainly because of a mulititude of errors human & mechanical so unless the speed is significantly over the nominated V speed then a stated Vfe for Eg is almost an advisory speed, just don't exceed it when the head honcho is right next to ya !
CW
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V 1 the maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance. V1 also means the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance
CAO 20.7.1B definitions:
V1 means the takeoff decision speed
V1 means the takeoff decision speed
Should you suffer an engine failure on the takeoff roll, V1 is the latest speed by which the pilot must recognise the failure and elect to abort the takeoff, in order to stop the aircraft in the remaining Accelerate-Stop Distance Available.
To recognise an engine failure at V1, the engine must therefore have failed before the aircraft reached V1.
If you recognise an engine failure at V1 and decide to abort, the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the aeroplane will therefore happen after V1.
V2 is, in the same paragraph, defined as
V2 means the initial climb out speed which is not less than the take-off safety speed
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Just to add to the confusion a bit more, the newer C182s have the following Vfe's:
10 deg @ 140Kt
20 deg @ 120Kt
30deg @ 100Kt
And the white arc starts at 100kt so it only covers the last stage.
In the types i've flown if the Vfe is different for different stages of flap then its usually placarded on the panel or next to the flap lever. Otherwise if Vfe is the same for all stages its just the top of the white arc.
Chek the placard and/or the manual and you cant go wrong i guess.
10 deg @ 140Kt
20 deg @ 120Kt
30deg @ 100Kt
And the white arc starts at 100kt so it only covers the last stage.
In the types i've flown if the Vfe is different for different stages of flap then its usually placarded on the panel or next to the flap lever. Otherwise if Vfe is the same for all stages its just the top of the white arc.
Chek the placard and/or the manual and you cant go wrong i guess.
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Lasiorhinus, thats the definition given by the people who certify the majority of aircraft that inhabit the airspace, and to whose standards the performance charts are produced. You will find a discussion at http://www.pprune.org/tech-log/32866...kts-prior.html
FAR 25 Transport Category Aircraft
§ 25.107 Takeoff speeds.
(a) V1 must be established in relation to VEF as follows:
(1) VEF is the calibrated airspeed at which the critical engine is assumed to fail. VEF must be selected by the applicant, but may not be less than VMCG determined under §25.149(e).
(2) V1, in terms of calibrated airspeed, is selected by the applicant; however, V1 may not be less than VEF plus the speed gained with critical engine inoperative during the time interval between the instant at which the critical engine is failed, and the instant at which the pilot recognizes and reacts to the engine failure, as indicated by the pilot's initiation of the first action (e.g., applying brakes, reducing thrust, deploying speed brakes) to stop the airplane during accelerate-stop tests.
As you can see from para (2) it is not the decision speed. V1 is the point at which the pilot initiates the abort.
Edited to add: Reading the CAO I wonder if CASA may be calling Vef the V1? Seems that may be the case from their statement that "failure of the critical engine so that it is recognised at V1". Of course they are entitled to mandate what ever they wish. JT will be able to give the definitive answer.
FAR 25 Transport Category Aircraft
§ 25.107 Takeoff speeds.
(a) V1 must be established in relation to VEF as follows:
(1) VEF is the calibrated airspeed at which the critical engine is assumed to fail. VEF must be selected by the applicant, but may not be less than VMCG determined under §25.149(e).
(2) V1, in terms of calibrated airspeed, is selected by the applicant; however, V1 may not be less than VEF plus the speed gained with critical engine inoperative during the time interval between the instant at which the critical engine is failed, and the instant at which the pilot recognizes and reacts to the engine failure, as indicated by the pilot's initiation of the first action (e.g., applying brakes, reducing thrust, deploying speed brakes) to stop the airplane during accelerate-stop tests.
As you can see from para (2) it is not the decision speed. V1 is the point at which the pilot initiates the abort.
Edited to add: Reading the CAO I wonder if CASA may be calling Vef the V1? Seems that may be the case from their statement that "failure of the critical engine so that it is recognised at V1". Of course they are entitled to mandate what ever they wish. JT will be able to give the definitive answer.
Last edited by Brian Abraham; 13th Sep 2008 at 11:49.
Second the comment about variations within the same type.
1977 C172N is limited to 85 KIAS for ALL flap extension whereas many other models (N/P/R/S) have a 10 deg speed limit of 110 KIAS.
Diff in POH and placarded next to flap lever/indicator.
1977 C172N is limited to 85 KIAS for ALL flap extension whereas many other models (N/P/R/S) have a 10 deg speed limit of 110 KIAS.
Diff in POH and placarded next to flap lever/indicator.
Brian, it seems to my reading the only difference is that the FAA assume the pilot can recognise the failure and begin to act in the same instant, while CASA only think we're capable of doing one thing per instant
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FAA assume the pilot can recognise the failure and begin to act in the same instant
§ 25.109 Accelerate-stop distance.
(a) The accelerate-stop distance on a dry runway is the greater of the following distances:
(1) The sum of the distances necessary to—
(i) Accelerate the airplane from a standing start with all engines operating to VEF for takeoff from a dry runway;
(ii) Allow the airplane to accelerate from VEF to the highest speed reached during the rejected takeoff, assuming the critical engine fails at VEF and the pilot takes the first action to reject the takeoff at the V1 for takeoff from a dry runway; and
(iii) Come to a full stop on a dry runway from the speed reached as prescribed in paragraph (a)(1)(ii) of this section; plus
(iv) A distance equivalent to 2 seconds at the V1 for takeoff from a dry runway.
(2) The sum of the distances necessary to—
(i) Accelerate the airplane from a standing start with all engines operating to the highest speed reached during the rejected takeoff, assuming the pilot takes the first action to reject the takeoff at the V1 for takeoff from a dry runway; and
(ii) With all engines still operating, come to a full stop on dry runway from the speed reached as prescribed in paragraph (a)(2)(i) of this section; plus
(iii) A distance equivalent to 2 seconds at the V1 for takeoff from a dry runway.
It then goes on to wet runway requirements. From a 737 manual, and note the decision speed comment,
V1 is the maximum speed for initiating an RTO. Therefore, the decision to stop must be made prior to V1.
V1 is often considered as the decision speed. This is incorrect because V1 is the speed at which the stopping actions must have been initiated.
· The decision to continue or reject a takeoff must have been made just prior to V1.
Therefore it is of importance that the V1 call is completed at the moment actual speed is at the V1 mark.
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A321 Vfo
A fully loaded A321 (at or close to MTOW) can exceed Vfo after takeoff with the autopilot on. The limit for flaps 1 or less, is 215 knots. At heavy weights, S-speed can be as high as 218 knots (above Vmo). The AutoRetract System operates at 210 knots, however this leaves only 5 knots before Vfo is exceeded. My company hands out QAR's for a 1 knot exceedance. They suggest we use selected speed to avoid this situation, however this doesn't work well, since Vls rapidly increases after flaps retract, and soon you find "selected speed" is Below Vls and could get into Alphafloor, which is another can of worms. What is Airbus' view on this...or anyone else who cares to comment ???????
Considering this is a GENERAL AVIATION forum....
Maybe you should be looking at another forum?
Maybe you should be looking at another forum?
Moderator
If you recognise an engine failure at V1 and decide to abort, the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the aeroplane will therefore happen after V1.
The comment is appropriate to a now long-abandoned philosophy.
For the past 30+ years Industry practice has been to adopt the heavy metal OEM philosophy of the go/stop paddocks being fenced by action. That is to say, in respect of V1 and decision making, if we haven't already started stopping .. then we're going. While this may not be the very best decision in all cases, as a general process it will result in the better outcome most of the time.
It is wise to keep in mind that the rules (as in Design Standards) have evolved (ie changed) over the years. In respect of ASD considerations the main change of note was Part 25 A/L 42 (1978) - for the Aussies, this was reflected in CAO 101.6 A/L 62 - which introduced the 2 second delay for new aircraft designs. This change took a lot of the heat out of the last few metres of the stopping process as the end of the runway loomed.
Historically, Australia has had some difficulty in aligning Airworthiness Standards and related Operational Requirements (CAO 20.7.1B) although things have been tidied up somewhat in recent years. Often we used to be driven to distraction by 101.5/6 and 20.7.1B conflict in the wordiology.
JT will be able to give the definitive answer.
That's probably somewhat more flattering than justified. Perhaps we can debate the subject when next enjoying a convivial ?
****
So far as flaps are concerned .. and we can talk generally in that it is very difficult to interpret the Design Rules (ie Part 23/25) in isolation. One MUST read them with the ACs, TCDS, and the FAA/OEM deals done during the certification process - the latter not generally being Public Domain. The result is that one really needs to rely on the AFM/POH having the definitive story for the pilot on the line.
Main thing with flaps ... regardless of the nitty gritty of what the limit means and how it should be interpreted for a given Type ... is that the OEM does not intend for the pilot routinely to select or operate at or near the limiting flap speed.
If you do, expect your maintenance folks to scream blue murder as you will needlessly be increasing your maintenance costs as the bits of tin break much earlier than they need to .. I routinely carry on a bit on just this topic as my pilots have a liking for going faster than I think they really need to ..
...and be aware that while you might get away with a flap overspeed, the next pilot may wear the consequences of your stupidity.
Probably a little alarmist.
While the limits are there for good reason and are not to be exceeded, an isolated modest flap overspeed isn't going to cause the flaps to fall off/apart.
However, if you are involved in an exceedance, please do write it up in the MR so that any relevant maintenance inspections can be effected post flight. If the exceedance is somewhat more than modest, there may be some rectification work to be done.
The comment is appropriate to a now long-abandoned philosophy.
For the past 30+ years Industry practice has been to adopt the heavy metal OEM philosophy of the go/stop paddocks being fenced by action. That is to say, in respect of V1 and decision making, if we haven't already started stopping .. then we're going. While this may not be the very best decision in all cases, as a general process it will result in the better outcome most of the time.
It is wise to keep in mind that the rules (as in Design Standards) have evolved (ie changed) over the years. In respect of ASD considerations the main change of note was Part 25 A/L 42 (1978) - for the Aussies, this was reflected in CAO 101.6 A/L 62 - which introduced the 2 second delay for new aircraft designs. This change took a lot of the heat out of the last few metres of the stopping process as the end of the runway loomed.
Historically, Australia has had some difficulty in aligning Airworthiness Standards and related Operational Requirements (CAO 20.7.1B) although things have been tidied up somewhat in recent years. Often we used to be driven to distraction by 101.5/6 and 20.7.1B conflict in the wordiology.
JT will be able to give the definitive answer.
That's probably somewhat more flattering than justified. Perhaps we can debate the subject when next enjoying a convivial ?
****
So far as flaps are concerned .. and we can talk generally in that it is very difficult to interpret the Design Rules (ie Part 23/25) in isolation. One MUST read them with the ACs, TCDS, and the FAA/OEM deals done during the certification process - the latter not generally being Public Domain. The result is that one really needs to rely on the AFM/POH having the definitive story for the pilot on the line.
Main thing with flaps ... regardless of the nitty gritty of what the limit means and how it should be interpreted for a given Type ... is that the OEM does not intend for the pilot routinely to select or operate at or near the limiting flap speed.
If you do, expect your maintenance folks to scream blue murder as you will needlessly be increasing your maintenance costs as the bits of tin break much earlier than they need to .. I routinely carry on a bit on just this topic as my pilots have a liking for going faster than I think they really need to ..
...and be aware that while you might get away with a flap overspeed, the next pilot may wear the consequences of your stupidity.
Probably a little alarmist.
While the limits are there for good reason and are not to be exceeded, an isolated modest flap overspeed isn't going to cause the flaps to fall off/apart.
However, if you are involved in an exceedance, please do write it up in the MR so that any relevant maintenance inspections can be effected post flight. If the exceedance is somewhat more than modest, there may be some rectification work to be done.
