Vintage Mooney PIC panel tilt

[MV Aviation]

Hi everyone,

What’s the reason that on all Vintage Mooneys without a „one piece windshield“ conversion, the pic avionics panel is tilted towards the pilot at the top? That seems to be the case even after panel restorations. 
 

The panel in my 65’E was redone some time in the past and doesn’t look to bad. I’m just in the process of getting two G5’s installed and I’d like to get a standard six pack layout. However, before I start dumping money into one or the other panel solution, I’d like to evaluate the best option.

I’ve opened the avionics top cover and looked behind the panel. It seems that for long instruments (such as my stec30 and Narco NAV), there are tubes of the steel cage in the way, in case the panel would be tilted back to be flush with the rest of the avionics. Another option would be to cut out the current panel out of its frame and put a new panel on top of it.

Any recommendations on which way to go and why?

thx Marco

[Ned Gravel]

I have a '65E as well with the older panel.  It has an 8 degree tilt forward.  If you do not, yours was modified to remove that tilt in the past.  If you want to be sure what your tilt is exactly, compare it with the tilt of the fore-aft line at the top of the external rear avionics bay (battery compartment) cover.  That is the supposed true horizontal line when the aircraft is in flight. 

With a protractor and a plumb bob, you will see what that is on the ground and be able to compare it with your panel.  The tilt forward on my panel is only 8 degrees when in level flight.  If I am not mistaken it is much closer to vertical when the aircraft is parked on the ground.  MIne sits very slightly nose up, but not as nose up as many others.

Compare @larrybLarry's Mooney at the end of the Caravan Parking spot during one of the Oshkosh Mooney Caravan camping sites with the second picture posted here.  It is my '65 E model.  His (along with many others in that photo) sits more nose up than mine.   9201A is an M20K Encore (long body) and mine is a '65 E model.

The third picture is my current panel.  You will note that it too was modified from the original, although not as much as yours.  The right side portion of my panel is the original version for my Mooney.

 

[MV Aviation]

Hi Ned,

thanks for your reply.

I think you misunderstood my question. I know that my entire panel ist tilted forward, the same way all vintage Mooneys came from factory. And the pilot side of the panel is tilted backward (similar to your panel), towards the pilot, as can be seen on the first picture of my original post.

My question now is: when I redo the pilot side panel only, do I have to keep the backward tilt, as it is shown in the picture (if yes, why?) or can I remove the light grey 3D panel construction in the picture and replace it with a 2D flat panel that is flush with the rest of the avionics?

[Ned Gravel]

Ah. I see.  Have you confirmed that it is tilted backwards from comparison with the horizontal on the avionics bay?  Or from its apparent tilt while parked.  If it is the latter, it may not actually be tilted.  

As for replacing it with another, your only concern will be the AI and the tilt it was configured for when installed. That was the issue that forced me to measure my own panel’s tilt back in 2008.  Other than ensuring sufficient clearance for instruments behind the panel, which should already be OK, you should be good.

But as Anthony says, just my opinion.  I am not a mechanic with the authority to tell you how this actually is supposed to work, only what I did.  

 

[chriscalandro]

Your gyro instruments need to be vertical. That’s why the bend is in the original panel. Retrofitted flat panels adjust to go vertical so they don’t lean back and leave a gap in the top. It doesn’t lean forward. 
 

Unless you put the bend in like the original, you will need that gap at the top and for the panel to be perfectly vertical. 

Edited November 14, 2020 by chriscalandro

[carusoam]

In 65, the panel was a shot gun layout...

There was a belt line / equator / bend in the panel...

Above the equator.... the panel was more or less vertical

Below the equator... the panel had the 8° offset, which is typical for mechanical gyros of the day...

This was done to minimize challenges of parallax.... allowing needles to appear centered, when they were centered...

 

Modern panels are being cut as one vertical piece, installed square to the plane...

Plane is leveled in two directions... using the sheet metal seam on the tail... and the seat rails in the cockpit...

Use caution when reusing gyros.... make sure they are 0° tilt gyros and not 8° tilt gyros...

If a gyro needs to be changed from one tilt to the other... an instrument shop can do this change...

 

PP thoughts only, not an instrument builder...

Best regards,

-a-

[MV Aviation]

Thanks for all your comments!

Since I'm getting rid of my mechanical gyros replacing them with G5s, I should not be forced to take care of such "old school" problems. The G5 installation manual allows up to 15° tilt. I'll have to check, how much the s-tec 30 turn coordinator can handle.

Installation depth is a problem in the Mooney. Not all instrument positions are equal in therms of protrusion, since there are steel tubes crossing behind the panel. E.g. I cannot move the Narco NAV unit from the bottom to the top position, unfortunately.

[chriscalandro]

7 hours ago, MV Aviation said:

I should not be forced to take care of such "old school" problems.

You would be surprised how many newer instruments require a 0degree vertical tilt.

[MV Aviation]

UPDATE

I've measured the angles of the panel relative to the Earth with the aircraft sitting on ground. It's not a fully scientific approach, but it has some meaning. 

Ok, sitting on the ground with a "nose up" attitude, the PIC panel already has a foreward tilt of 3° from the vertical axis (of the Earth, not the aircraft). This might reduce by 1° or 2°, when the nose tire is pumped up a little more. The rest (avionics stack and co-pilot panel) have a 11° forward tilt in that attitude. So, there's that famouse 8° difference, which is stated everywhere else.

What surprises me is that the PIC panel seems to already have a forward tilt on the ground. The aircraft attitude in level cruise will be more nose down than this, hence, the tilt angle will only increase (I guess to somewhere around 11° for the left panel and to 19° for the right panel). I expected the left panel to be close to 0° in level flight.

Can anyone clarify?

[MV Aviation]

And another Update...

I just found out that the S-TEC turn coordinator requires a certain panel tilt angle, which is designated in it's part number. It can be modified for different angles by the manufacturer, but the price tag is pretty steep. Meaning, I need to keep my angle.

[chriscalandro]

On 11/14/2020 at 9:21 PM, chriscalandro said:

You would be surprised how many newer instruments require a 0degree vertical tilt.

 

[carusoam]

MV,

Did you also measure the angle of the horizontal seam on fuselage... near the avionics access panel?

This is the standard location for measuring horizontal variation...   I ASSume this is horizontal in flight...

But know it can’t be perfect, since AOA will change based on WnB...

Best regards,

-a-

[hammdo]

The tilt is measured with the plane leveled as it is in flight. I then used a digital angle finder to confirm 0° tilt. The service manual shows where you ‘level’ the plane to do the measurement...

I had to do that when I installed a rebuilt attitude indicator in my old B.

-Don

 

[Stanton R]

I have a 63C. I made the pilot panel the same angle as the copilot panel which is technically to much of an angle for the G5, however I have a Aspen and a G5 and have had no problems with them. Your big problem will be the Stec.

 

I would also take the shock mount out of what you have.

[Nukemzzz]

Believe it or not I’ve found that the modern IPhone is pretty capable of measuring the plane tilt at the avionics bay seam, and it’s even more capable of laying against the panel face to measure its angle. Delta between the two is the panel tilt. 

[MV Aviation]

On 1/13/2021 at 6:48 AM, carusoam said:

Did you also measure the angle of the horizontal seam on fuselage... near the avionics access panel?

Negative. What I've measured no is this:

                              PIC panel angel          SIC panel angel

On ground            3° forward                   11° forward

In flight                 6-7° forward                14-15° forward

So, neither panel has 0°, neiter in flight nor on the ground. The left panel might reach 0° (and even negative °), when I pull up the nose on takeoff or flair on landing. That it is only 3-4° nose down from ground to level flight, surprised me a little. I expected a bit more.

According to its PN, the STEC TC requires a 0° installation.

3 hours ago, Nukemzzz said:

Believe it or not I’ve found that the modern IPhone is pretty capable of measuring the plane tilt at the avionics bay seam, and it’s even more capable of laying against the panel face to measure its angle. Delta between the two is the panel tilt. 

Guess what, that's how I measured it ;-)

[Nukemzzz]

I'm going to speculate wildly here because its an interesting topic, however, this is outside of my expertise and experience....

Remember that W&B changes the in-flight angle of attack.  You can change the in-flight panel tilt by moving stuff fore and aft in the cabin. Also, if you slow down the plane enough you can make that 6-7degress closer to 0.

I suspect that avionics manufacturers set the gages up so they work across typical AOA ranges using "level on the ground" as the stable point of reference since you can't achieve this reliably in the air with any specifications because there are too many factors in play (speed, W&B, rigging, etc).

It sounds like your PIC is tilted too far forward, but the only way to know for sure is to compare with the avionics bay level reference seam as that is what they are talking about when STEC says 0 degrees.  

Side note: I set my PIC panel tilt when the engine was out of the plane and the tail was on the ground.  I had to set it for 10degrees negative.  lol