Flap Extension Speeds

[N201MKTurbo]

They don't do much anyway, why all the fuss?

[mooniac15u]

3 hours ago, m20kmooney said:

Is anyone else disturbed by this thread or is it just me? Are folks actually using flaps to slow down? And is there really so much confusion about Vfe?

Vfe IS THE HIGHEST PERMISSIBLE SPEED WITH FLAPS IN A PRESCRIBED EXTENDED POSITION. This speed is going to be higher for T/O flaps and lower for any setting beyond T/O. It’s spelled out in the POH. For example my POH says this speed is 132 KIAS for T/O setting and 115 KIAS for ANY SETTING BEYOND T/O, i.e. 15° to full down. 

Can you post that section of your POH?  The TCDS says 109 KIAS for all serial numbers of M20K.

 

Airspeed Limits S/N 25-0001 thru -0889 25-1000 and Up
Maneuvering 135 m.p.h. (117 kts) IAS 123 KIAS
Never exceed 225 m.p.h. (195 kts) IAS 195 KIAS
Flaps extended 125 m.p.h. (109 kts) IAS 109 KIAS
Landing gear retraction 122 m.p.h. (106 kts) IAS 106 KIAS
Landing gear extension 150 m.p.h. (130 kts) IAS 140 KIAS
Landing gear extended 150 m.p.h. (130 kts) IAS 165 KIAS
Maximum structural cruising 200 m.p.h. (174 kts) IAS 174 KIAS

[Marauder]

1 hour ago, mooniac15u said:

Can you post that section of your POH?  The TCDS says 109 KIAS for all serial numbers of M20K.

 

Airspeed Limits S/N 25-0001 thru -0889 25-1000 and Up
Maneuvering 135 m.p.h. (117 kts) IAS 123 KIAS
Never exceed 225 m.p.h. (195 kts) IAS 195 KIAS
Flaps extended 125 m.p.h. (109 kts) IAS 109 KIAS
Landing gear retraction 122 m.p.h. (106 kts) IAS 106 KIAS
Landing gear extension 150 m.p.h. (130 kts) IAS 140 KIAS
Landing gear extended 150 m.p.h. (130 kts) IAS 165 KIAS
Maximum structural cruising 200 m.p.h. (174 kts) IAS 174 KIAS

I went through the TCDS as well. I was hoping that it would shed some additional insight on the topic. Instead, it confirmed what I believe is true, that the flap speed limitations on Mooneys is dictated by the TCDS based on serial number and these will be reflected in your POH. I did see a few anomalies which I will mention later.

For A/B models there appears to be only one flap setting 21.5 degrees and it is limited to 100 MPH / 87 KIAS

Beginning with the C models, you will see the 15 and 33 degree flap settings. Up to serial #680001, the flap speed is limited to 100 MPH / 87 KIAS, SN680002 up to 700091 & 20-0001 & up are limited to 125 MPH / 109 KIAS

E models up to 690001 have the same lower VFe of 100 MPH / 87 KIAS, from SN 690002 to 700061 and 21-0001 & up have the higher 125 MPH / 109 KIAS VFe

First anomaly. There is a posted VFe for F models after 1965 that shows it to be 105 MPH / 91 KIAS. Then the TCDS shows up to SN 680001 the VFe is 125 MPH / 109 KIAS. There is no mention about later model VFe speeds.

Second anomaly. All J models are subject to the VFe of 110 KIAS with one exception. SN 24-3000 through 24-3078 are the only planes that have two separate speeds listed. Those planes will be allowed to deploy 15 degrees of flaps at 126 KIAS and the VFe for full flap extension is 110 KIAS. Where it gets stranger is that the POH for this model (I think it is the 1986 model year) is called out separately than other Js. So obviously something happened to those planes where the partial deployment at higher speeds was allowed. After serial number 3078, it resorts back to the 110 KIAS limitation.What is even stranger is the airspeed placard for these serial numbers (3000-3078) also calls out in note g this:

g. On M20J (24-3000 through 24-3078) above flap switch: "FLAP EXTENSION SPEED MAXIMUM, 15°, 132 KIAS; FULL, 115 KIAS.

This ironically doesn't match what they said the POH should say.

K models are limited to 109 KIAS

L/M/R/S models have a 110 KIAS VFe and interestingly flap settings of 10 degrees and 33 degrees.

So there you have it. Too bad Bill Wheat isn't here to participate. I am sure there is some history there. Based on what I read, I think the safe thing to do is operate the flaps either partial or full extension with VFe as the speed limitation. Unless of course you own a J with a serial number from 3000 to 3078.

 

Edited January 29, 2019 by Marauder

[mooniac15u]

29 minutes ago, Marauder said:

I went through the TCDS as well. I was hoping that it would shed some additional insight on the topic. Instead, it confirmed what I believe is true, that the flap speed limitations on Mooneys is dictated by the TCDS based on serial number and these will be reflected in your POH. I did see a few anomalies which I will mention later.

For A/B models there appears to be only one flap setting 21.5 degrees and it is limited to 100 MPH / 87 KIAS

Beginning with the C models, you will see the 15 and 33 degree flap settings. Up to serial #680001, the flap speed is limited to 100 MPH / 87 KIAS, SN680002 up to 700091 & 20-0001 & up are limited to 125 MPH / 109 KIAS

E models up to 690001 have the same lower VFe of 100 MPH / 87 KIAS, from SN 690002 to 700061 and 21-0001 & up have the higher 125 MPH / 109 KIAS VFe

First anomaly. There is a posted VFe for F models after 1965 that shows it to be 105 MPH / 91 KIAS. Then the TCDS shows up to SN 680001 the VFe is 125 MPH / 109 KIAS. There is no mention about later model VFe speeds.

Second anomaly. All J models are subject to the VFe of 110 KIAS with one exception. SN 24-3000 through 24-3078 are the only planes that have two separate speeds listed. Those planes will be allowed to deploy 15 degrees of flaps at 126 KIAS and the VFe for full flap extension is 110 KIAS. Where it gets stranger is that the POH for this model (I think it is the 1986 model year) is called out separately than other Js. So obviously something happened to those planes where the partial deployment at higher speeds was allowed. After serial number 3078, it resorts back to the 110 KIAS limitation.What is even stranger is the airspeed placard for these serial numbers (3000-3078) also calls out in note g this:

g. On M20J (24-3000 through 24-3078) above flap switch: "FLAP EXTENSION SPEED MAXIMUM, 15°, 132 KIAS; FULL, 115 KIAS.

This ironically doesn't match what they said the POH should say.

K models are limited to 109 KIAS

L/M/R/S models have a 110 KIAS VFe and interestingly flap settings of 10 degrees and 33 degrees.

So there you have it. Too bad Bill Wheat isn't here to participate. I am sure there is some history there. Based on what I read, I think the safe thing to do is operate the flaps either partial or full extension with VFe as the speed limitation. Unless of course you own a J with a serial number from 3000 to 3078.

 

FWIW those serial numbers for the J's were designated as 205's.  They were only produced in 1987 and 1988 and were limited to those serial numbers.  I don't know what was different about 205's.

[Releew]

If your speed is in the White Arc you're fine.  Little Flap, Lots of Lift.  A Lot of Flap, Lots of Drag.......  With full Flaps, Mooney's do very well on a steep approach.  If the approach is flat it will take 15in of MP Plus depending on Load to maintain Level Flight.  As a common practice, I to land with the first flap (take off) position in case I need to exercise a go around.  There are so may factors to consider....  Clearing and obstacle on a short strip is one.....  If there is plenty of runway and the approach is unobstructed the first flap position is all that needed. If you have to execute that go around, with a load, you will be glad that's all the flap you had dialed in....

[Chris K]

2 hours ago, Marauder said:

I went through the TCDS as well. I was hoping that it would shed some additional insight on the topic. Instead, it confirmed what I believe is true, that the flap speed limitations on Mooneys is dictated by the TCDS based on serial number and these will be reflected in your POH. I did see a few anomalies which I will mention later.

For A/B models there appears to be only one flap setting 21.5 degrees and it is limited to 100 MPH / 87 KIAS

Beginning with the C models, you will see the 15 and 33 degree flap settings. Up to serial #680001, the flap speed is limited to 100 MPH / 87 KIAS, SN680002 up to 700091 & 20-0001 & up are limited to 125 MPH / 109 KIAS

E models up to 690001 have the same lower VFe of 100 MPH / 87 KIAS, from SN 690002 to 700061 and 21-0001 & up have the higher 125 MPH / 109 KIAS VFe

First anomaly. There is a posted VFe for F models after 1965 that shows it to be 105 MPH / 91 KIAS. Then the TCDS shows up to SN 680001 the VFe is 125 MPH / 109 KIAS. There is no mention about later model VFe speeds.

Second anomaly. All J models are subject to the VFe of 110 KIAS with one exception. SN 24-3000 through 24-3078 are the only planes that have two separate speeds listed. Those planes will be allowed to deploy 15 degrees of flaps at 126 KIAS and the VFe for full flap extension is 110 KIAS. Where it gets stranger is that the POH for this model (I think it is the 1986 model year) is called out separately than other Js. So obviously something happened to those planes where the partial deployment at higher speeds was allowed. After serial number 3078, it resorts back to the 110 KIAS limitation.What is even stranger is the airspeed placard for these serial numbers (3000-3078) also calls out in note g this:

g. On M20J (24-3000 through 24-3078) above flap switch: "FLAP EXTENSION SPEED MAXIMUM, 15°, 132 KIAS; FULL, 115 KIAS.

This ironically doesn't match what they said the POH should say.

K models are limited to 109 KIAS

L/M/R/S models have a 110 KIAS VFe and interestingly flap settings of 10 degrees and 33 degrees.

So there you have it. Too bad Bill Wheat isn't here to participate. I am sure there is some history there. Based on what I read, I think the safe thing to do is operate the flaps either partial or full extension with VFe as the speed limitation. Unless of course you own a J with a serial number from 3000 to 3078.

 

I just went through the TCDS as well and what is published there does not match the AFM for my first Mooney which was a '77 J model, serial number 24-0306.  The AFM indicates both the Vfe limitation and normal operations for full flaps as 115 KIAS.  For a moment I thought maybe due to differences of KCAS vs. KIAS on that specific J, however looking at the TCDS, it refers only to IAS, not CAS.  Only thing I could think of that differed with the early J's vs. later J's was that mine had the fully variable flap switch (not sure if motor was different as well). 

Somewhere I once heard that documentation standards during the busy GA boom from the 50's through early 80's was not what it is today, especially since the advent of electronic word processing makes updating and tracking changes easier.  That could possibly explain some minor variations and difficulty of keeping AFM and TCDS consistent/updated, however that higher published partial flap extension in the TCDS is unique for the 3000-3078 series of J's.  Why would Mooney publish for those particular aircraft and not others?  Surely if the V model is now limited to 110 KIAS for all flap settings and if Mooney intended to limit partial flap extension for older models as well, are they not obligated to publish AFM revisions for the applicable models? 

 

[jaylw314]

1 hour ago, Releew said:

If your speed is in the White Arc you're fine.  Little Flap, Lots of Lift.  A Lot of Flap, Lots of Drag.......  With full Flaps, Mooney's do very well on a steep approach.  If the approach is flat it will take 15in of MP Plus depending on Load to maintain Level Flight.  As a common practice, I to land with the first flap (take off) position in case I need to exercise a go around.  There are so may factors to consider....  Clearing and obstacle on a short strip is one.....  If there is plenty of runway and the approach is unobstructed the first flap position is all that needed. If you have to execute that go around, with a load, you will be glad that's all the flap you had dialed in....

My CFI had me practice go-arounds with full flaps and full fuel during my transition training.  We weren't at gross, but he's a big guy so we were heavy enough.  He wanted to drill in my head that the plane will, in fact, start climbing with gear down and full flaps, so you don't need to frantically clean the plane up immediately--add power, fly the plane first, THEN start the go-around checklist.

Nowadays, I pretty much land with full flaps routinely.  I might use half-flaps only for practice or for significant crosswinds.

[PT20J]

A long and interesting discussion. I'll try to summarize the facts:

1. 14 CFR Part 1 states "V_FE means maximum flap extended speed." If only a single V_FE is specified, then it applies to all flap extensions. No other interpretation makes sense because it would require the maximum speed for other than full extension to be unspecified.

2. The TCDS defines the conditions for airworthiness. Pilots generally do not reference the TCDS, so the airworthiness conditions pertinent to operation are included the Airplane Flight Manual Limitations section. This section is regulatory and binding on the pilot.

3. Flaps do four things: 1) They increase C_Lmax while reducing the angle of attack at which C_Lmax occurs, 2) They decrease the angle of attack at which zero lift occurs, 3) They increase drag, 4) They create a pitching moment.

4. Mooney flaps are more effective at reducing stalling speed than flaps on many similar GA airplanes.  To prove this to yourself, look up the V_s0 and V_s1 speeds (calibrated) for various airplanes. (Or, find the other thread where I did this).

5. The primary purpose of flaps is not to slow down. However, they do create drag. Should you forget to raise flaps after takeoff,  your first indication may well be in inability to attain cruise speed.

6. There is no mechanism in any Mooney to raise the flaps in the event of an overspeed.

Skip

[carusoam]

Nice summary, Skip!

Great document review, Marauder!

Best regards,

-a-

[Yetti]

On 1/29/2019 at 7:33 AM, N201MKTurbo said:

They don't do much anyway, why all the fuss?

My hero!

[byrdflyr]

The POH of my 1985 K model says: Vfe - Maximum Flap Extended Speed - KCAS 109 (KIAS 112) - "Do not exceed this speed with flaps in full down position."  The gear speeds (VLE and VLO) are both 132 KIAS.  Gear retraction speed is much slower - 107 KIAS.   I think just about everyone will, at some point, forget to retract the flaps or gear.  I have not seen any posts confirming damage resulting from flap or gear overspeeds resulting from the "after takeoff" scenario (gradually building speed) - which I think would be very different than an overspeed dumping the gear or flaps into the wind in the approach phase.  Does that make sense?

 

[PT20J]

I believe the gear retraction speed limit is to reduce strain on the motor/gearbox. When retracting, you have gravity and air loads working against you. It's pretty apparent with the J-bar.

The flap actuating mechanism has a lot of flex. Lots of us have admitted to getting distracted and failing to retract takeoff flaps with no apparent damage. It's pretty apparent when the airplane doesn't accelerate to cruise speed. 

Skip

[Ragsf15e]

3 hours ago, PT20J said:

I believe the gear retraction speed limit is to reduce strain on the motor/gearbox. When retracting, you have gravity and air loads working against you. It's pretty apparent with the J-bar.

The flap actuating mechanism has a lot of flex. Lots of us have admitted to getting distracted and failing to retract takeoff flaps with no apparent damage. It's pretty apparent when the airplane doesn't accelerate to cruise speed. 

Skip

Maybe not damage specially attributable to flap overspeeds, but the “flex” you mentioned in the flap mechanism is often cited as a factor in cracking near the stub spar where the flap tubes connect.  There’s an expensive SB that deals with adding a doubler there if it’s cracked.  I think it only applies to vintage airplanes.  Having someone (who will never again step foot within a 50’ radius of your airplane) step on the flap when climbing onto the wing may also be a cause.  Either way, I wouldn’t test the limits.  Damage might not be apparent but it might still be expensive!

Edited September 6, 2019 by Ragsf15e

[PT20J]

16 minutes ago, Ragsf15e said:

Maybe not damage specially attributable to flap overspeeds, but the “flex” you mentioned in the flap mechanism is often cited as a factor in cracking near the stub spar where the flap tubes connect.  There’s an expensive SB that deals with adding a doubler there if it’s cracked.  I think it only applies to vintage airplanes.  Having someone (who will never again step foot within a 50’ radius of your airplane) step on the flap when climbing onto the wing may also be a cause.  Either way, I wouldn’t test the limits.  Damage might not be apparent but it might still be expensive!

Certainly agree with that. The Mooney flap mechanism is not very robust. I probably should have been more clear: exceeding the flap and/or gear speeds once in a great while doesn't seem to hurt anything, but those speeds aren't arbitrary and continued abuse will eventually take its toll.

[carusoam]

On 9/6/2019 at 11:39 AM, byrdflyr said:

 

.  I have not seen any posts confirming damage resulting from flap or gear overspeeds resulting from the "after takeoff" scenario (gradually building speed) - which I think would be very different than an overspeed dumping the gear or flaps into the wind in the approach phase.  Does that make sense?

 

Look for pics of spar cracks around here.  They are related to the flaps experiencing over speeds...

Unfortunately there is no detail of how it gets cracked, or how big the over speed was, or if it occurred during flap operations, or just having them down...

Forces get greater as the flaps deploy more... they get greater with the square of airspeed as well...

The fix is essentially a doubler on the spar that supports the flaps...

As far as gear goes... with manual gear... the limit is how fast the handle rips through the cockpit... fast enough it smacks the instrument panel and gets a bend in it... 

it is hard to mess with the gear themselves... but gear doors seem to get out of alignment every now and then... or just get torn...

Fair advice... don’t get in the way of the gear handle while it rips through the cabin... it will be like getting hit by a steel bat...

For electric gear... same forces apply... but control arms have a tendency to get bent instead...

So...

We have been given limitations that have been proven to keep things from bending and breaking... and then we have the greater unknowns...

In between... we have some data generated later, that wasn’t covered for the same structures earlier...

and...

looking at the variations of forces... airspeed causes things to get powerful... but smacking into mechanical limits is  also capable of causing different damage... this is why the limitations are written for things that are deployed and things getting deployed or getting stowed...

So...

We get options like... Choose the type of damage you want to risk or just stay within the proven limitations... 

PP thoughts only, not a CFI or mechanic...

 

Best regards,

-a-

[Aerodon]

The 172's up to an M model had 'infinitely variable' flap settings with an indicator a a VFE=85kts.  The N model onwards have no indicator, but a 'stepped' flap selector.  So the first 10 degrees allows VFE=110kts, a 29% improvement over the 85KTS limitation for 40 degrees flaps.  Interestingly enough, there is no further reduction from the 85kts for the 172's with 40 flaps vs. 30 flaps.

My Seneca has flap extention speeds as follows:  10/140 KIAS, 25/122 KIAS, 40/115 KIAS.  And very definitive notches on the flap lever. A 22% improvement in range.

The Seneca has a 130 gear extension speed, and the residual thrust of 2 engines has the effect of making it quite hard to slow down.  I remember once been cleared for the ILS at KBFI while I was still 50nm out.  It was fun cruising down the GS at 180kts until I couldn't slow down.  I eventually had both engines at 15", the gear warning going off and had to level off, slow down, get gear and all the flaps out, then dive bomb the GS from above.  Spoilers would be nice.

So from a stress point of view, My K has a VFE of 109 its, but it is the same wing and flap system as the J model with the 125KIAS limitation for 10 degrees.  Some might extrapolate that this will be OK in a K model, provided you have a way of accurately determine the 10 degree mark.

Aerodon

 

 

 

 

 

[0TreeLemur]

On 9/6/2019 at 4:13 PM, Ragsf15e said:

Maybe not damage specially attributable to flap overspeeds, but the “flex” you mentioned in the flap mechanism is often cited as a factor in cracking near the stub spar where the flap tubes connect.  There’s an expensive SB that deals with adding a doubler there if it’s cracked.  I think it only applies to vintage airplanes.  Having someone (who will never again step foot within a 50’ radius of your airplane) step on the flap when climbing onto the wing may also be a cause.  Either way, I wouldn’t test the limits.  Damage might not be apparent but it might still be expensive!

I had a MSC do the annual on our '67 C a few years ago.   They noted that the doubler was added as per the SB and a fine job at that.

[PT20J]

40 minutes ago, Aerodon said:

So from a stress point of view, My K has a VFE of 109 its, but it is the same wing and flap system as the J model with the 125KIAS limitation for 10 degrees.  Some might extrapolate that this will be OK in a K model, provided you have a way of accurately determine the 10 degree mark.

Only the 205s had the higher speed for partial flaps, and it was for 15 degrees. There were only 79 of those built. After that, Mooney went back to the 110 KIAS flap speed for the M20J. 

[kortopates]

All the G1000 long bodies also have a flap detent position for takeoff position but Mooney did not certify them for a higher partial flap speed. So although a switch with a detent position is a prerequisite for a higher partial flap extension the manufacturer must also document it in the TCDS, like they did for the very limited number of late J’s.


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[GeeBee]

Because it is a CAR 3 airplane, Mooney only needs to define max Vfe at full flaps and no other positions despite the existence of such positions. If it were an FAR 23 airplane, they could not do so and would have to described max Vfe at each available position. As it is, partial flap Vfe is not defined on many Mooney aircraft. It is a "Sgt Schultz" approach to certification.

If you look at CAR 3 airplanes such as the Cessna 182R it only lists the full flaps max Vfe on the TCDS despite the 182R having higher partial flaps placarded in the cockpit. 

[Pinecone]

10 hours ago, PT20J said:

Only the 205s had the higher speed for partial flaps, and it was for 15 degrees. There were only 79 of those built. After that, Mooney went back to the 110 KIAS flap speed for the M20J. 

But was there anything really different for the 205?

[PT20J]

4 hours ago, Pinecone said:

But was there anything really different for the 205?

I don’t think do, but the fact that Mooney didn’t carry this forward suggests to me that perhaps they decided it wasn’t a good idea.

[kortopates]

4 hours ago, Pinecone said:

But was there anything really different for the 205?

Yes, a flap switch with a detent position for take off flaps, unlike the rest of the fleet till prior to G1000's.

[Scottknoll]

Not sure if it helps, but I have a flap switch with a takeoff detent. 1998 Ovation 1 sn29-0135

[Niko182]

1 minute ago, Scottknoll said:

Not sure if it helps, but I have a flap switch with a takeoff detent. 1998 Ovation 1 sn29-0135

Same here. 99 Eagle 30-0010