Speed brake max speed with long range tanks?

[FloridaMan]

I can't find anything showing a deployment limitation in my documents or placards, but on the Precise Flight website, it says:

• Deployable at any speed below Vne (175 Knot limit if you have tip tanks)

However, it says this for all planes (Bonanzas, etc). I have the long range tank STC, but these are not "tip tanks." I'll call PreciseFlight and ask, but curious if there's any tribal knowledge on this subject here. 

[Stnelson903]

Definitely post the answer. I have that arrangement.


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[Bryan]

Vne = airframe “never exceed” speed, red line on your indicator. Tip tanks on Bo’s change VNE.

[carusoam]

M20R with PF speed brakes... deploy as necessary..... technically they have a Vne documented limitation...

Mooney wing with 100gal tanks... probably the same for 130gallons in the tanks.....

Slow to gear speed to deploy the gear....

Increase speed to gear down speed...

Pull the MP back...

Push the prop full forwards...

You will be on the ground in a few minutes...

The descent rate is that fast....

The faster the plane is moving, the more effective the brakes are...

 

I have done this once during Transition Training... it is a unique experience that is a worthwhile practice event...

Old PP memories only... check your POH for a few pages from Precise flight...

Consider what you would do if turbulence has thrown you past Vne... do you  pull the power and raise the nose and wait...?

Or do you deploy the speed brakes with that?

If turbulence is that strong... I would want to be below Vna.... waiting may not be an option.

 

Off kilter PP thoughts only, not a CFI...

Best regards,

-a-

[Oldguy]

The only thing I see in my Supplemental section on the speed brakes operating limitations is "Airspeed: Same limitations as basic airplane.".

Very descriptive.

[larryb]

For my encore there is no limit on speed brake usage. Any airspeed is fine.

[FloridaMan]

On 8/22/2018 at 10:31 PM, carusoam said:

M20R with PF speed brakes... deploy as necessary..... technically they have a Vne documented limitation...

Mooney wing with 100gal tanks... probably the same for 130gallons in the tanks.....

Slow to gear speed to deploy the gear....

Increase speed to gear down speed...

Pull the MP back...

Push the prop full forwards...

You will be on the ground in a few minutes...

The descent rate is that fast....

The faster the plane is moving, the more effective the brakes are...

 

I have done this once during Transition Training... it is a unique experience that is a worthwhile practice event...

Old PP memories only... check your POH for a few pages from Precise flight...

Consider what you would do if turbulence has thrown you past Vne... do you  pull the power and raise the nose and wait...?

Or do you deploy the speed brakes with that?

If turbulence is that strong... I would want to be below Vna.... waiting may not be an option.

 

Off kilter PP thoughts only, not a CFI...

Best regards,

-a-

That brings up another question that might have a counter-intuitive answer. If speed brakes are more effective at higher speeds, do you descend faster at higher speeds with the brakes deployed -- at a higher rate and/or over distance covered? Controller gives you an instruction to cross a fix at a much lower altitude. Do you pop the brakes and pull the power, or are your chances better keeping your speed up to increase brake effectiveness? 

[Bryan]

I use the speed brakes as an "extra" boost to basically give me an extra 500fpm (at higher speeds) without power config changes or reduce my speed about 15-20kts in a few seconds.  I normally don't pop speed brakes and pull power.  I normally use the speed brakes to keep power in and give me a better decent to let me slowly work the power out as-needed or use the speed brakes to get to my gear speed of 140kts quickly.  I tend to "stay fast" until 1000 ft AGL and then I can throw speed brakes to get to gear speed, throw gear out to really slow down, and then finally flaps for a stabilized approach.

[StevenL757]

On 8/22/2018 at 9:29 PM, Antares said:

I can't find anything showing a deployment limitation in my documents or placards, but on the Precise Flight website, it says:

• Deployable at any speed below Vne (175 Knot limit if you have tip tanks)

However, it says this for all planes (Bonanzas, etc). I have the long range tank STC, but these are not "tip tanks." I'll call PreciseFlight and ask, but curious if there's any tribal knowledge on this subject here. 

Not sure about any limitation for Bonanzas, but Precise Flight speed brakes on all Mooney models can be operated up to and including Vne regardless of whether standard or long-range tanks are fitted.

Steve

[Bryan]

I always thought of the speed brakes a tiny parachute like devices that block the wind and hold it back pulling on the airframe.  What I have come to realize, thru research and experience, is they disrupt the wind over a portion of the wing making it less efficient with less lift.  The surface area of what is actually blocking the wind is not as big as I thought. 

[carusoam]

On 8/24/2018 at 7:40 AM, Antares said:

That brings up another question that might have a counter-intuitive answer. If speed brakes are more effective at higher speeds, do you descend faster at higher speeds with the brakes deployed -- at a higher rate and/or over distance covered? Controller gives you an instruction to cross a fix at a much lower altitude. Do you pop the brakes and pull the power, or are your chances better keeping your speed up to increase brake effectiveness? 

You will descend faster....  2000+ vertical feet per minute or much more..... unfortunately my VSI pegs at 2kfpm so I don’t have an exact answer....

It still takes knowing your systems to demonstrate how best to handle it....

Essentially you are using up the maximum amount of energy possible having everything deployed....

This is done ‘safely’ at gear down speed.  Following the procedure to deploy brakes, slow to gear op speed, then lower the gear.... once the gear is down... increase speed to gear down speed....

You wouldn’t slow to drop flaps to use up even more energy.... Somebody did the proof indicating gear and speed brakes use up the most energy, using that high speed...

 

To get a feel of the effectiveness of the brakes at speed... and how they become more effective with more speed...

Using the car example... stick your hand out the window at 35mph, then again at 70mph.... it is a lot more than 2X the braking power... more like 2²X....

 

Now for the How does this really work? part.... 

1) the brakes interrupt air flow across about 3’ Of wing span on each side...

2) this effectively removes 6’ Of wingspan’s worth of lift....

3) the pilot balances the loss of lift by increasing the AOA... controlling Airspeed...

4) The increase of AOA takes a huge amount of energy from the system....

5) With the engine MP pulled all the way back, the only way to keep the plane traveling at gear down speed is to descend...

6) keep in mind this is an E procedure... to be used to be on the ground in a few minutes...

7) Applying this to ordinary flight because a controller asked you to.... may take some significant adjustments....

8) Are you trying to be friendly to your engine?  A minimum MP to maintain CHTs would be expected... this adds energy to the system...

9) Are you flying with the gear up still? Maximum braking is going to occur with maximum speed...

10) all this talk of maximums.... makes me kind of uneasy... like discussing performance T/Os and landings....

Let me know what I have missed...

Don’t experiment without full knowledge of how the systems are supposed to perform.  Use a CFI for that...

PP thoughts only, not a CFI....

Best regards,

-a-

[N201MKTurbo]

You want to see the VSI spin, slow to gear speed, lower the gear, put out the speed brakes and do a commercial spiral. It will come down at 3500 FPM.

[Oldguy]

This is a video showing the effect of speed brakes on a Mooney wing with enough rain/water to define their area of disruption on the wing. Thought it was fairly impressive.