'90 M20J Book Speed

[joepilot]

I don't have a POH in front of me.  Can someone please tell me what the book says a 1990 M20J running 24"/2400, 50ROP, around 6500', KTAS should be? (about 68% power I figured, and kinda in the "red box", but those are the #'s I was given) Not sure what the inflight weight was, but probably a few hundred under gross.

 

Thanks a lot!

 

-Joe

 

PS I've tried to do a Forum search, but didn't have much luck.

[Jeff_S]

Well, you've left some variables like temperature out of the equation, but the book example in the POH says that 65% power at 6000' and temperature of 20°C is 155 KTAS.  So if you think you're getting slightly greater power in your test, and you're a skosh higher, then it would be a bit higher than that.  Other factors to consider are what prop you have on it, as the book is based on the standard McCauley 2-blade.

 

Here's a link to an online POH for a J, in case you want to do more research: http://www.deltaaviationllc.com/Nav%20Page/POH/M20J%20POH3203B.pdf

[Danb]

Jim I don't think it's the marketing...I had a 1977 J and would get about 150 knots at joes numbers and I had a new 1988 and would get close to 160 knots at the same numbers, I flight planned my 1988 J about 8 knots higher than my 1977 model. I guess the one piece belly and other small improvements done over the 10-15 years made the difference. Even a good wax job helps a little....

[Bob_Belville]

Unless you fly near gross wt. you should expect to beat the book speed for gross (2740/2900). I'm a little faster than that in my old E but I'm usually @ 2300-2500#.

[Bartman]

I plan on 145 Kts at about 60-65% LOP in my 1977 J. I can get about 153 Kts with max power at about 7000 Ft, but temps run high so I don't use that setting. Some say they only loose a couple of Kts going LOP. That has not been my experience.

I used to see 158 Kts with max power at optimal altitude when I first acquired my J. Since then the engine mounts were replaced and I now have a drooping engine about 1/2 inch where the spinner meets the cowl. Plans are to get the engine mounts shimmed at next annual. Since the engine has more hours I'm not sure if the reshimming will get me back to 158. We will see.

One other time I had a drop in airspeed was when I had the inner gear doors off. Without going into that and long story short I lost about 8-10 Kts while they were off. As I recall the POH stated I would lose 5Kta,again that was not my experience. Regained it when they were reinstalled.

[aaronk25]

So at 6500 on my 77j my 4 way average at 100rop max rpm, full throttle is 162kts.

6500 at 9.2 gallons per hour 65-70% is 154kts lop

6500 at 8.2gph 55-59% is 147-148kts....

Ball centered.

The new planes have 20 degrees worth of timing where the dual mag is set at 25 degrees. I think there similar in speed maybe with a slight edge on the newer J, but I find 8kts hard to believe.

I also have one piece belly but the one with the ribs, so it's not as smooth as the flat one piece. Step removed, no under belly strobe. Updated prop to round tip but I don't think it' adds to any speed increase. I'm fact I think the square tip it originally came with was one knot faster as the round too is really wide prop.

All speeds 4 way average. Nothing to special about my plane....

[preinke]

My inner gear doors are bent and cracked and not installed . What is required to replace them with non aluminum ?

Paul '77J KIKV

[cliffy]

Paul, I don't know how one could do that. Don't know of any STC to do that.