Newb - 196 mph possible in SWTA mod F ?

[sreid]

Quote: garytex

Jetdriven:  Thanks, I'll keep looking.  I also stand in front of the refrigerator "where'se the milk?"

Gary

[xftrplt]

Ross,

I would think you're right, but, especially on my first coffee, I'm a literal kind of guy and take a post for what it says.

I believe on my K there is no separate pitot-static source (other than the Alt Static), but I'll check this morning. No offense intended. 

[jetdriven]

Actually I goofed.  The Mooney airspeed does have two ports on the rear.  Somehow I didnt know that. 

[xftrplt]

Quote: xftrplt

Sorry, Jose, I still disagree--at least in practice.

Theoretically, massive static leak in the cabin, i.e., a disconnected line, just might give a slightly high indication if  the cabin were underpressurized, which, in a Mooney, I can't see happening.

Most likely, the cabin pressure would be slightly greater than at the flush static port, hence a lower A/S indication.

Theory vice practice.

[N44AB]

I had my airspeed indicator dial repainted and calibrated by my local instrument shop. I replaced the instrument and had the shop check for system leaks. It was determined that there was a pitot leak. After a little trouble shooting we found the leak was coming from the pitot system drain at the underside of the pilot side wing. The drain is a spring loaded valve that uses an "O" ring to seal the system. My "O" ring was shot, cracked in multiple places and falling apart. I'm guessing that it was the original "O" ring. Unfortunately the valve is a pain to get to. The pilot side lower interior panel has to be removed to access the valve which is buried behind tube framing and a couple of large wire bundles. It's a pain... but doable. Anyway, thought I'd post my experience with all the talk of system leaks in this thread.

75 M20F

[testwest]

+1 for drain valve repairs. We are going through ours from stem to stern while doing our JPI/Aspen/G430W/(Brittain)/(KX170B)/(KNS80) upgrade. BOTH our pitot and static drains were leaking and required overhaul.

LASAR to the rescue, again!

They sell an overhaul kit, it is really a new metal spring and o-ring, under $10. Labor will be more because you need to drill out 4 rivets to remove the valves.

We are going through our alternate static source valve too, and replacing all of the polyflo fittings in the pitot and static plumbing with the new nylon ones like on the latest M20s.

Because of the research work we are getting ready to do in our J, I want the pitot-static system to be absolutely perfect. We have already run the analog ASI and altimeter through an instrument shop for calibration, and the Aspen is going to get the same checks, before install.

Good luck with that F. Welcome to Mooney ownership. You just made a whole bunch of new friends who are as smart and practical as you are.

[N601RX]

For any planes with the Brittain Altitude hold there will always be a small leak in the pitot. This is a design feature and therefore you must remove the line and cap it before testing the pitot for leaks.

[Lood]

I'm sure my F won't get 19" MP at 11,500ft. I haven't been that high, but my MP is just over 19" at 9500ft, IIRC. Could it have something to do with my old engine? Compressions were not bad though.

[Ned Gravel]

Quote: Lood

I'm sure my F won't get 19" MP at 11,500ft. I haven't been that high, but my MP is just over 19" at 9500ft, IIRC. Could it have something to do with my old engine? Compressions were not bad though.

[Hank]

Quote: edgargravel

Really?  Mine was reading almost 22" at 9000' last week.  Why the difference?

[Shadrach]

Quote: Hank

Really?  Mine was reading almost 22" at 9000' last week.  Why the difference?

[Lood]

I agree that mine is low, but that's the facts. To confirm, I just had look through my files and pulled the Gami lean test results. Here goes:

OAT 50 deg F; pressure alt: 6500ft; WOT; 2430rpm; MP 21.7"

If you do the simple thumbsuck calculation on MP that decrease by 1"/1000ft increase in alt, mine will sit at 16.7" at 11,500ft. At 8500ft, I normally got a MP of around 20". Just for interest sake, my TAS is/was also lowish - 138 - 140 kts. However, my brand new engine was delivered to my AME yesterday and they are installing it as we speak. I must confess, I am like a little child - absolutey overboard with exitement and anticipation. My Mooney should be ready to fly by next week Thursday and I will most certainly share my joy after I brought it home.

[Hank]

Quote: Shadrach

Something isn't right here . . . Lood's plane needs to get checked! I run my C at 20" at 10,000; only been to 11,000 in cruise once or twice, clearing mountain turbulence, and just took what I got and was happy.

Compressions won't have anything to do with MP, just with power produced. MP is the atmospheric pressure minus any losses between the air intake and the manifold, which shouldn't be more than 2-2½". Something somewhere isn't right--air filter clogged, tubing cracked or coming off would be my first guesses.

[Shadrach]

Quote: Hank

Something isn't right here . . . Lood's plane needs to get checked! I run my C at 20" at 10,000; only been to 11,000 in cruise once or twice, clearing mountain turbulence, and just took what I got and was happy.

Compressions won't have anything to do with MP, just with power produced. MP is the atmospheric pressure minus any losses between the air intake and the manifold, which shouldn't be more than 2-2½". Something somewhere isn't right--air filter clogged, tubing cracked or coming off would be my first guesses.

[SkyPilot]

I went on to Fairmont Hotsprings in BC last October and cleared the mountains at 17.5 " at 14,500'. I had my ram open and at that altitude I think it gave me less than an extra inch.

[Lood]

Hank, I don't have ram air on my 'F. I find this discussion very informative - especially the possibility that there might have been an induction leak somewhere on my engine. I never thought anything about my MP being lower than normal untill I read this thread. I'll compare the MP of the new engine to that of the old one and I'll also see how it compares to those in my POH.

[danb35]

Lood, has the ram air been removed from your plane?  It was standard on the '67 F.

[Lood]

Hi Dan, yes it has been removed completely and the opening in the cowling has been riveted closed with an aluminum plate. It was very well done - almost unnoticeable. The control inside the cockpit was also removed. Even if it was still installed, I doubt whether I would have used it. I live in a dry and windy part of SA with lots dust and I would rather cautious to use it. The idea of sucking unwanted dust, etc into my engine scares me somewhat. Normally, I also don't fly very high - usually 6500 - 7500ft and that's around 3000ft AGL where I live.

[jetdriven]

Given the restriction in the airbox, can you put a Challenger filter on there?  We have a J and changed from the Brackett to the Donaldson and i swear it gave us a half inch.   That may not be accurate, but our WOT fuel flow went up a half to a full gallon per hour, so there is more air passing through. I'd bet it is a good bang for the Rand on an F.

[garytex]

Had the ASI tested, it reads 7 mph high around 80 mph, and 5 mph high at 150.   Well that explains some of the fast speeds.  Additionaly, I have been flying final at 80 mph indicated, and the plane just splats on to the runway with absolutely no float.  It also feels like it is in a very low energy state just before the flare.  Like the bottom could easily fall out if provoked even the tiniest little bit.  Well no kidding, at 73 mph on final, and slowing slightly in the roundout. 

[kellym]

Quote: garytex

Had the ASI tested, it reads 7 mph high around 80 mph, and 5 mph high at 150.   Well that explains some of the fast speeds.  Additionaly, I have been flying final at 80 mph indicated, and the plane just splats on to the runway with absolutely no float.  It also feels like it is in a very low energy state just before the flare.  Like the bottom could easily fall out if provoked even the tiniest little bit.  Well no kidding, at 73 mph on final, and slowing slightly in the roundout. 

[garytex]

Yeah, it's on the list.  There is no static leak which was also checked. I really want to put a true airspeed indicator in so I can compare true to ground and check on winds aloft as I climb.   Additionally I was looking at my manual and evidently there is some overregistering going on as part of the ASI / Pitot / Static instalation from the factory.  I am going to have to wait a while, as the fund is pretty skinny after purchase and then bring to reasonable condition repairs.  I flew yesterday, and was again impressed with how fast the thing is.  I just got lucky with a straight airframe, and mods that actually work, I think.

Thanks again to everyone for input as I settle in mooneyworld.

Gary 

[kellym]

Quote: garytex

I really want to put a true airspeed indicator in so I can compare true to ground and check on winds aloft as I climb.

[garytex]

It's hot enough here in Texas that the temprature correction can be significant, and the last one I had also corrected for altitude.  Oh I just looked at your address, AZ, so I probably don't have anything to tell you about heat.  At 8500 the other day it was showing high 160s at 20dC, 5mph of that overregister.  Still, zipping along.

I'm a happy boy,

Gary