J Speeds

[mike_elliott]

2 minutes ago, bradp said:

I was trying to figure out why - for a plane with a nearly identical engine, fuel servo etc., how it could be getting a TAS that seemed quite high while supposedly running LOP. Gsrxpilot is absolutely right that LOP or ROP doesn't determine an absolute CHT number. Also right that you can't infer where you are on the mixture curve based on CHT alone.

However since I run the same engine and presumably have a similar airframe I can infer that those CHTs are not typical for LOP (meaning, say -10 F for the richest cylinder) or even peak mixtures at that altitude and RPM/MP combination. They seem high and in this case they are due to inadequate air cooling. I'd have to actually try hard running maybe 25-50 ROP to get those CHTs at that alt MP and RRM combination. That's why I was questioning where he was on the mixture curve.

I think, based on whatever data we've consumed, that most of us will subscribe to the idea that the cylinder pressure and CHT will be lower for a given value LOP as for the same value ROP.


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The 84 frame is faster than a 77, as they have a few clean up mods as standard, like the smooth belly. What is really weird about N984VW is that it was also slightly out of rig (see turn coordinator) and DMAX tried to bring her back in, but it was slightly off still. It had to do with a right aileron repair at some point and it wasn't quite "square". If this sucker wasn't "dog walking" as it blasts along, it could ekk out a few more kts TAS I am sure. Don countered the issue with lowering the lt. flap a smidgeon, but that didn't help the speed one bit.

[aaronk25]

The 84 frame is faster than a 77, as they have a few clean up mods as standard, like the smooth belly. What is really weird about N984VW is that it was also slightly out of rig (see turn coordinator) and DMAX tried to bring her back in, but it was slightly off still. It had to do with a right aileron repair at some point and it wasn't quite "square". If this sucker wasn't "dog walking" as it blasts along, it could ekk out a few more kts TAS I am sure. Don countered the issue with lowering the lt. flap a smidgeon, but that didn't help the speed one bit.

Hey ya wanna race? Calling my 77 slow?


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[mike_elliott]

1 minute ago, aaronk25 said:

 

 

 

 

Hey ya wanna race? Calling my 77 slow?


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naw....you got that power flow  guaranteed for 20 kts more at 10 GPH less. Do I get to use the Bravo?

[aaronk25]

Ha ha lol....no you leave that bravo in the hanger, I don't need that bad of a bruised ego.


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[Bennett]

Wouldn't it be fun to have a Mooney race by model -- something like the old Sun and Fun 60 mile triangular race. Back in the early 90s I raced my 261 in that race and won the 200-250 HP class . I still have that trophy on my hangar.


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[kmyfm20s]

Take a formation clinic and I think you all will be surprised with the variation in air speed indicators between planes. You need to do a good 3 way air speed calibration with the GPS to get your airspeed. With my past J I planed for 155 Kts and 9.5 GPH and always got there faster and had more fuel remaining. I would say I was closer to 158 Kts and 9 GPH.

[cnoe]

10 hours ago, mike_elliott said:

The 84 frame is faster than a 77, as they have a few clean up mods as standard, like the smooth belly. What is really weird about N984VW is that it was also slightly out of rig (see turn coordinator) and DMAX tried to bring her back in, but it was slightly off still. It had to do with a right aileron repair at some point and it wasn't quite "square". If this sucker wasn't "dog walking" as it blasts along, it could ekk out a few more kts TAS I am sure. Don countered the issue with lowering the lt. flap a smidgeon, but that didn't help the speed one bit.

 

I've been pondering your numbers and was glad to see the smooth belly mentioned. How about the step? And do you know if the elevator lines up cleanly with the horiz stab? I also noticed that the MAP was pretty high for 9.5K and 14 C.; the induction on that baby must be super-clean. I assume the ram-air is open and perfectly aligned with the cowl. At 25 F. LOP and 9.5 K I can believe the 8.5 gph, but 158 TAS is incredible on only ~127 HP. Go Mooney!

If it stands up to the 3-way groundspeed test feel free to put my name in the jealous column.


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Edited November 23, 2016 by cnoe
Edited for math error, duh. Thanks Mike!

[aaronk25]

Step? Oh forgot to say also I removed the step. Probably worth 1 or 2 knots. I think all the little things add up.


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[N9201A]

Seems things like which year, smooth belly, step/no step, rigging and the like really do make the difference that we read about before buying. So does sliding your seat back!

In my experience, there is no substitute for flying alongside another aircraft to resolve any disparities. One more benefit of form flying ...


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[Mooney in Oz]

6 hours ago, aaronk25 said:

Step? Oh forgot to say also I removed the step. Probably worth 1 or 2 knots. I think all the little things add up.


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I recall many years back on the Mooney email list, former Mooney factory test pilot Bob Kromer commented on removing the step. He said when he was at the factory, for testing purposes he flew a Mooney (can't recall the model) with the step removed and all the test equipment rigged up. The end result was a speed gain of not more than half a knot.

Not worth it.

Victor

[ArtVandelay]

9 hours ago, mike_elliott said:

That's the real reason to run LOP. It helps when the baffles are right  

I thought it was to keep the engine clean, lower emissions, maximize MPG.

[mike_elliott]

9 hours ago, bradp said:

6 hours ago, cnoe said:

 

 

I've been pondering your numbers and was glad to see the smooth belly mentioned. How about the step? And do you know if the elevator lines up cleanly with the horiz stab? I also noticed that the MAP was pretty high for 9.5K and 14 C.; the induction on that baby must be super-clean. I assume the ram-air is open and perfectly aligned with the cowl. At 25 F. LOP and 9.5 K I can believe the 8.5 gph, but 158 TAS is incredible on only ~114 HP. Go Mooney!

If it stands up to the 3-way groundspeed test feel free to put my name in the jealous column.


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MP gauge could have been off a tick back then, I don't recall, just that it I was WOT so it was what it was. No Ram air, as that doesn't add much at all on a J as you know. On my old F, with the induction in a low pressure area, Ram air is a different story. What I do know is that I have flown over 3 dozen J models and this is the fastest (or most efficient) one so far. N9124P came close, but was a bit more gravity challenged and not quite up to the task. Filter was new that day. the step is still on her. At 25 LOP 8.5 GPH * 14.9= 126.65 HP, but I seriously doubt if this tired old motor was cranking at full efficiency. Hey guys, this isn't my plane to wag my weenie about, I am just a paid observer!

[cnoe]

23 minutes ago, mike_elliott said:

At 25 LOP 8.5 GPH * 14.9= 126.65 HP, but I seriously doubt if this tired old motor was cranking at full efficiency.

My bad. The only thing worse than a typo is a math error. Thanks for correcting it.

And from what I understand even a tired engine makes good HP, and that sounds like the case here. As I recall TCM did some testing on engines purposely set up with low compression (leaky rings?) that pretty much made book power.

So when you determine exactly what makes N984VW so fast please PM me with the details. I promise I won't share them with anybody else. 

[wishboneash]

There was a thread a while ago which talked about "Slow Js" and I had included some of my numbers in that thread.

My '78J is comparatively slow seeing the numbers being posted on MS. Somebody has to be on other side of the bell curve I guess! 

 

[aviatoreb]

On 11/23/2016 at 2:52 PM, cnoe said:

My bad. The only thing worse than a typo is a math error. Thanks for correcting it.

I call that a "matho".

[mike_elliott]

My bad. The only thing worse than a typo is a math error. Thanks for correcting it.
And from what I understand even a tired engine makes good HP, and that sounds like the case here. As I recall TCM did some testing on engines purposely set up with low compression (leaky rings?) that pretty much made book power.
So when you determine exactly what makes N984VW so fast please PM me with the details. I promise I won't share them with anybody else. 

I wish I knew, I could start a speed mod business! It must have to do with the cleanliness of that particular airframe over others I have flown. I hope the new paint doesn't negatively impact it for Joe. New interior is next up for this (now) beauty.

[Bob - S50]

6 hours ago, wishboneash said:

There was a thread a while ago which talked about "Slow Js" and I had included some of my numbers in that thread.

My '78J is comparatively slow seeing the numbers being posted on MS. Somebody has to be on other side of the bell curve I guess! 

 

It wouldn't hurt to have your airspeed indicator checked.  When we got ours it was off by as much as 8 KIAS at some speeds.  You may be going faster than you think.

[ArtVandelay]

6 hours ago, wishboneash said:

There was a thread a while ago which talked about "Slow Js" and I had included some of my numbers in that thread.

My '78J is comparatively slow seeing the numbers being posted on MS. Somebody has to be on other side of the bell curve I guess! 

 

Looking at your avatar it looks like landing gear isn't fully stowed, hard to tell from low resolution picture. 

[wishboneash]

19 minutes ago, teejayevans said:

Looking at your avatar it looks like landing gear isn't fully stowed, hard to tell from low resolution picture. 

That's a good point. My airframe definitely needs to be looked at with all the antennas and gaps that need checking as well. Attached picture is the best I can find. Perhaps the left main shows something awry.

To Bob S-50's point, I have checked ground speeds in various directions, calibrated against known winds, as well as flown formation and know that my plane is definitely slow. 5 or more knots is quite a bit and I hope to get to the bottom of this. I can check with Top Gun to see if they can find something in the rigging or otherwise. Engine parameters look to be normal so I don't think the engine is tired.

Thanks.

[bradp]

I know that my right gear door hangs down 1/4 inch or so. Every AP I've asked about this has not wanted to go fishing. Including MSC. Say it's not worth starting from the beginning re rigging the gear. I've gone along so far and just left it be.


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[Andy95W]

The main gear doors are adjustable without changing the gear rigging.  There are two adjustable rods that attach the door to the gear leg.

I'm surprised the MSC didn't want to try this.  Once it's on jacks, it would probably only take about 15 minutes.

[bradp]

The main gear doors are adjustable without changing the gear rigging.  There are two adjustable rods that attach the door to the gear leg.
I'm surprised the MSC didn't want to try this.  Once it's on jacks, it would probably only take about 15 minutes.

I'll take a look tomorrow when I'm out at the hangar. It could be that they're already adjusted maximally.


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[ArtVandelay]

38 minutes ago, N1395W said:

The main gear doors are adjustable without changing the gear rigging.  There are two adjustable rods that attach the door to the gear leg.

I'm surprised the MSC didn't want to try this.  Once it's on jacks, it would probably only take about 15 minutes.

Also I was told if gear pucks are out of spec it will result in gear doors not closing. All MSCs are not created equal.

[N9201A]

Also I was told if gear pucks are out of spec it will result in gear doors not closing. All MSCs are not created equal.

And they may leave telltales. Had an annual at which mechanic who saw telltales on both sides, equally spaced, said "oh, you hit something"...uh, no, but now I know I need a new mechanic! Thanks!

[cleatus99]

1982 Model, I get about 155KTAS WOT at 2400, 7500'

 

 

Edited November 27, 2016 by cleatus99
Updated yr