Define Vfe

[airaholic]

Flap extention speed does this apply to partial or full flap? eg can partial flap be extended above vfe?

[Muffinman]

Maximum Flap Extension/Extended Speed - (several values depending on aircraft type and the position of extension) -do not extend or operate with flaps in prescribed position above these speeds.

[Cap'n Arrr]

If the aircraft has a different Vfe for different flap settings, then obey those individually. If it only has one, common sense dictates that flaps must be UP above this speed, and can be lowered below it. While small flap settings probably put less stress on it, just be smart and make sure that no flaps are down above Vfe

[future.boeing.cpt]

Indeed

e.g. A PA34-200T Seneca2 has a flight manual stated VFE of 107kts although 10degrees can be put down at 138kts and 25degrees put down at 121kts. The full 40 can be extended in the white arc (below 107kts).

Maybe this changes for different aircraft, but I assume that VFE is for full flap extension.

[knox]

Some 172's have high speed flaps. From memory first stage (10deg?) can be taken at 110kts which is well above top of white arc.

I think similar applies in the 206 too. Once again, from memory 10deg at 140kts (i think top of Vno was 150kts).

But consult the manual (don't assume it will be the same for all a/c), it will reveal all.

Knox.

[solowflyer]

I had always understood it was no flap down above the white arc however different people have told me otherwise that it is ok to put 10 deg out above white arc to help slow ac down and others have said vfe is for full flap.

[brns2]

solowflyer... read your flight manual. Dont take anyones word.

As i recall i think some cessnas... 172,182 you can take the first 10 degrees above the white arc, but below the specified airspeed in the flight manual

Also regarding post #1. You refer to Vfe as flap extension speed, which is technically wrong. Vfe is flap EXTENDED speed.

Flap extension speed is refered to as Vfo or flap operating speed (as the flap comes down)

[knox]

Vfo... never heard of it and can't seem to find any reference to it - except in electronics.

Brns2 - Can you supply more tangible information on Vfo.

Knox.

[Muffinman]

brns2 - send Beechcraft an email and tell them their B200 flight manual is wrong. Yeh as you pointed out - don't take anyones word for it:rolleyes:

[solowflyer]

If vfe is the flap extended speed that sounds to me like flap is fully extended

[compressor stall]

It's all about semantics, but the different manufacturers are talking the same thing.

I currently fly two very different transport cat aircraft types -

Type 1:

Vfe = "Maximum Flap Extended Speed or Operating Speed"
Flap 2 (15deg)=200kts, Flap 3 (20deg)=185kts, Flap full (40deg) =177kts.

Type 2:

Flap Extended Speeds
The maximum permissible airspeeds for extending the wing flaps and for flight with the flaps extended
(VFE) are:

To/App (10deg)- 135kts, ldg (40deg) 115kts.

The common theme is that it's the maximum speed at which you can extend them or accelerate to with them already extended.

C210 drivers beware - different models have different flap speeds. From memory N series had a flap speed of 156 kts for the first stage. I never found out what the physical difference was compared to earlier models.

[Muffinman]

Exactly - it still seems some manage get their VFE approach and full down semantics mixed up with the VLO (extension and retraction) and VLE (extended).

Don't hold your breath Knox - it could be a while - brns2 has gone off to do some reading.

[brns2]

Far out you get shot down in here very quickly

Well i had a look in a beechcraft manual and their definition for Vfe is:
"Maximum flap EXTENDED speed is the highest speed permissible with wing flaps in a prescribed EXTENDED position"

So to me this means its a limit when they are in their extended position, not as you are putting them down in the transition. To me that is a operating speed referenced as Vfo. The beechcraft manual doesnt have Vfo (maybe it doesnt require it as it cant cause structural damage if the Vfe speed is complied with?)

I could not find a referance in any manual to Vfo, so i did a search for "Vfo airspeed limitaions" on the www and came accross the same definitions as i suggested. Heres one page i found on V speeds:

V1 | Take-off decision speed
V2 | Take-off safety speed (minimum)
Va | Design maneuvering speed
Vb | Design speed for maximum gust
Vc | Design Cruising speed
Vd | Design Diving speed
Vdf/Mdf | Demonstrated Flight diving speed
Vf | Design Flap speed
Vfc/Mfc | Maximum speed for stability Characteristics
Vfe | Maximum Flap Extended speed
Vfo | Maximum Flap Operating speed
Vh | Maximum speed in level flight with maximum continuous power
Vle | Maximum Landing gear Extended speed
Vlo | Maximum Landing gear Operating speed
Vlof | Liftoff speed
Vmc | Minimum Control speed
Vmca | Air Minimum Control speed
Vmcg | Ground Minimum Control speed
Vmo/Mmo | Mach, Maximum Operating limit speed
Vmu | Minimum Unstick speed (liftoff)
Vne | Never Exceed speed
Vno | Maximum structural cruising speed
Vpw | Pilot Window open speed
Vr | Rotation speed
Vref | Reference speed
Vs | Stalling speed
Vs1 | Stalling speed in a specified configuration
Vso | Stalling speed in the landing configuration
Vsse | Safe Single-Engine speed (render an engine inop)
Vtos | Take-Off Safety speed
Vtoss | Take-Off Safety speed category "A" rotorcraft
Vww | Windshield Wiper operating speed
Vx | Best angle of climb speed
Vxse | Best angle of climb speed, Single Engine
Vy | Best rate of climb speed
Vyse | Best rate of climb speed, Single Engine

[Muffinman]

No bullets intended brns2 - only shooting blanks these days anyway:{

Interesting table of Veees - and to think all this time I was trying to reach a V TOSS when really it was a V TOS:confused:

[brns2]

Well maybe i am wrong and so are the others that differ between Vfe and Vfo.

But do you not differ between a Vlo and a Vle?

Beechcraft manual specificaly says Vfe is an EXTENDED speed limit

Disregarding any manual, and just thinkingn about it with some commonsense, possibly some aircrafts design are so the flaps are not as strong in the transition as they are in their extended positions, these are the ones that have a Vfo stated?

[knox]

Sorry Brns2, Wasn't taking the pi55, I was genuinely interested.
Not everyone on here is trying to "shoot" ya down.


Knox.

[aileron_69]

Its different for different aircraft and its usually placarded beside the lever. i see a few references to 172s there. That depends on the model. The 172P can take 10 degrees at 110kts, the rest in the white arc. The piper archer by comparison you arent permitted to put any flap down until in the white arc. The 210 is model dependent too. In my L model i can take 10 degrees at 140kts, and throw the wheels out then too, but no more flap til the white arc, but in later models such as the M and N, you can throw out 10 flap and wheels at 165, at the top of the green arc.
So there is no hard and fast answer for all a/c types. As someone says, read the Flight Manual, its all in there. Most likely in the most illogical place in the flight manual imaginable if its a cessna one:E

[Cap'n Arrr]

I don't understand what the problem is really. If the flight manual says you can lower X flaps at Y speed, then you can do that. If it isn't in the flight manual, then don't do it!:ugh:

I had always understood it was no flap down above the white arc however different people have told me otherwise that it is ok to put 10 deg out above white arc to help slow ac down and others have said vfe is for full flap.Lowering flaps outside the Flight Manual prescribed Vfe for that flap setting is a no no. If someone needs to bust flap limits to slow down, that probably says more about their speed control than anything else.:=

It's like saying "I just want to get there a bit faster, so I'll fly a little above Vne." It isn't done.

The only time you can lower flaps outside the white arc is when the particular aircraft has down a different Vfe for 10deg flaps. For example, a Duchess can lower (from memory) up to 20deg of flaps, at a speed higher than on the white arc, but that flap setting still has a limiting speed placed on it, it just happens to be slightly higher than the white arc, which is the limiting speed for >20deg flaps.

If the flight manual only gives ONE flap extension speed, then above this speed no flap is to be extended. If the flight manual gives different speeds for first stage and other flap, then extend no flaps above highest speed, only extend first stage below first stage speed, second stage below its prescribed speed etc.

brns2 et al: If you think about it another way, as soon as the flaps leave the full up position, they are extended in someway, even if they are also in transit.

[aileron_69]

You hit the nail on the head Capt'n Arrr!!:ok:

[Brian Abraham]

Muffinman, tis the trouble with finding information on the net, no such thing as Vtos, stick with the Vtoss :ok: The FAA definitions follow

V A design maneuvering speed

V B design speed for maximum gust intensity

V C design cruising speed

V D design diving speed

V DF/ M DF demonstrated flight diving speed

V EF the speed at which the critical engine is assumed to fail during takeoff

V F design flap speed

V FC/ M FC maximum speed for stability characteristics

V FE maximum flap extended speed

V FTO final takeoff speed

V H maximum speed in level flight with maximum continuous power

V LE maximum landing gear extended speed

V LO maximum landing gear operating speed

V LOF lift-off speed

V MC minimum control speed with the critical engine inoperative

V MO/ M MO maximum operating limit speed

V MU minimum unstick speed

V NE never-exceed speed

V NO maximum structural cruising speed

V R rotation speed

V REF reference landing speed

V S the stalling speed or the minimum steady flight speed at which the airplane is controllable

V S0 the stalling speed or the minimum steady flight speed in the landing configuration

V S1 the stalling speed or the minimum steady flight speed obtained in a specific configuration

V SR reference stall speed

V SRO reference stall speed in the landing configuration

V SR1 reference stall speed in a specific configuration

V SW speed at which onset of natural or artificial stall warning occurs

VTOSS takeoff safety speed for Category A rotorcraft

V X speed for best angle of climb

V Y speed for best rate of climb

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

V 2 takeoff safety speed

V 2min minimum takeoff safety speed

It's interesting that in the regs (design criteria for Part 23 and 25 aircraft) there is no such thing as Vfo mentioned. Only Vf and Vfe. Where does this Vfo get mentioned? Flight manual?

To airaholic, the official FAA definition of Vfe is maximum flap extended speed, and the answer to "can partial flap be extended above vfe?" the answer is a resounding NO. Follow your particular flight manual. The Vfe may vary depending on the amount of flap - Chieftain for example, 162 kias up to 25° of flap, then 132 kias to 40°

[Capt Wally]

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 !:ok:



CW:)

[Lasiorhinus]

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


With respect, no, it's not.

CAO 20.7.1B definitions:
V1 means the takeoff decision speedV1 is the speed at which the decision to continue or abort the takeoff will be made.
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

[gettin' there]

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.

[Brian Abraham]

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/328668-call-v1-3-5kts-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.

[MakeItHappenCaptain]

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.

[Lasiorhinus]

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:ok:

:E

[Brian Abraham]

FAA assume the pilot can recognise the failure and begin to act in the same instant
Lasiorhinus, the FAA don't believe pilots are quite that God like. To simplicate, the engine fails at Vef - pilot realises some thing amiss (eg blown tires or engine failure) - pilot determines problem (engine failure) - knowing problem and still below V1 decides abort - pilot actions the abort - stomp brakes (this is the V1 point - certified performance is based on manual braking, not autobrakes), thrust levers retard etc etc

§ 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.

[AirbusBoeing2]

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 ???????

[MakeItHappenCaptain]

Considering this is a GENERAL AVIATION forum....

Maybe you should be looking at another forum?

[Sunfish]

...and be aware that while you might get away with a flap overspeed, the next pilot may wear the consequences of your stupidity.

[john_tullamarine]

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.

[AerocatS2A]

This thread is over 4 years old guys.

[john_tullamarine]

.. slow news day.