M20J vs M20J Takeoff Performance

[midlifeflyer]

I'm in a flying club with access to 3 M20Js. Two are pre-1991 (2740 MGTOW) and one is post 1991 (2900 MGTOW). In planning a trip for this weekend, I came across something curious:

 

The 2740 model POH has takeoff performance charts for both "normal" and for "max performance" takeoffs. The 2900 model POH only shows numbers for "normal" takeoff performance. And there doesn't seem to be a reference to an adjustment factor for the later model.

 

Is there a reason for this? Is there a generally-accepted adjustment among experienced Mooney pilots?

[Hank]

I don't fly a J or an IO-360, and my gross is well under 2740 lb, but I only have 2 takeoff modes--normal [no flaps], and near gross [with Takeoff flaps]. Other than flap position, everything is the same; away from my 3000' home field, runway length is rarely an issue, and we have trees at both ends at home, too.

 

Why do you feel the need for a "max performance" takeoff? How does it differ from normal? Push everything forward, rotate at 65-75 mph [for my plane], positive rate gear up, flaps up if used, accelerate to Vy after clearing obstructions. Climb speed will be partially determined by OAT, as that affects Oil Temp [my limiting factor during hot weather] and CHT. Climb to cruise altitude, trim. accelerate, set power, lean and retrim. Simple, easy, and I can be trimmed at 9000' in less than 15 minutes from engine start. You should easily beat me to altitude. Who needs a max performance takeoff? Stand on the brakes until full power, then release them?

[carusoam]

Find the thead titled something like over gross...

It is a recent discussion on the same or related topic.

The airplane requires a few things to be able to handle higher weights physically and legally.

(1) wing/lift capability.

(2) structure strength.

(3) power.

(4) STCs.

As the weight goes up, it's performance lessens. The POH of the older plane does not automaticaly apply to the newer plane.

Mooney seems to have indicated that by leaving out some capability while they increased the MGTOW.

the J has a lot of capability when comparing to a lessor powered Cessna. But it runs out of the power that is required to carry desired extra weight.

Fully loaded and short runways do not go together.

Mooney demonstrated it with the J, and again, with the Eagle and Ovation. And again with the O3 and Screamin' Eagle.

Without additional HP, runways get shorter and climb performance becomes dismal, trees get gigantic...

So operating at MGTOW at long runways (5,000’)with short trees is one thing, but short runways (2,000') and tall trees is significantly different.

The changes from one J to the newer one didn't increase the HP. For that, you can consider a Missle mod.

Mooney didn't accidentally leave out some important information, they left out the important performance. But they do leave it to you to operate wisely.

There is no substitute for cubic inches - Don Garlits?

Take-off is a drag race. You and your machine against the laws of physics. Get Don Garlits in your corner.

I like to operate with excess runway. If I'm not off the ground at the halfway point, I have time to stop and figure out what went awry. 85kias with trees in the windshield is an uncomfortable fealing...

This is solely my opinion and not a recommendation. YMMV.

Best regards,

-a-

[midlifeflyer]

Why do you feel the need for a "max performance" takeoff? How does it differ from normal? 

Other than the fact that the POH has them both?

 

Does a couple of hundred at sea level  to about 1000' of obstacle clearance difference depending on density altitude count?

[midlifeflyer]

As the weight goes up, it's performance lessens.

Mooney seems to have indicated that by leaving out some capability while they increased the MGTOW.

the J has a lot of capability when comparing to a lessor powered Cessna. 

Not necessarily. I know airports I would take a 172 into that I wouldn't take the higher weigh Mooney J.

 

But I'm not talking over gross.  The takeoff performance numbers for the 2470 MGTOW Mooney are substantially better than for the 2900 MGTOW Mooney given the identical actual weight.  So I'm not sure that the maximum capable weight is itself the issue. And, as I explained in response to Hank's post, the lower 50-ft target airspeed in the 2470 Mooney's max performance takeoff chart can be substantially better than it's "normal" counterpart. 

 

I've found that to generally be true in the dozen or so different makes/models I've flown - short field takeoff configuration and target airspeed performance is generally better tha non short field configuration and target airspeed performance.  

 

btw, yes, I read the over gross "discussion" thread. Didn't see anything particularly relevant to my "why is is different" question there.

 

 

 

I like to operate with excess runway. If I'm not off the ground at the halfway point, I have time to stop and figure out what went awry. 85kias with trees in the windshield is an uncomfortable fealing...

 

Me too. That's why I'm curious about this.

[carusoam]

Midlife,

I must be misunderstanding your question then...

Are you asking..

Why is there a difference in performance charts between both Js, at identical weights and HP?

That's an interesting question then.

High performance take-offs are another issue. Everything working as the POH requires, including the pilot.

Best regards,

-a-

[Hank]

The takeoff performance numbers for the 2470 MGTOW Mooney are substantially better than for the 2900 MGTOW Mooney given the identical actual weight.  So I'm not sure that the maximum capable weight is itself the issue. And, as I explained in response to Hank's post, the lower 50-ft target airspeed in the 2470 Mooney's max performance takeoff chart can be substantially better than it's "normal" counterpart. 

 

Lift is proportional to speed. If you want to take off at 2900 lbs, you must go faster than at 2740 lbs. The J's with increased gross also weigh more empty [due to installed equipment, improved insulation, wingtips, a thickened frame member, and general weight gain over the years]. For climb, they must have a slightly higher angle of attack, which will further slow them.

 

For obstruction clearance, if there's something 1000 agl to worry about, I would turn . . . and I am based and travel around in the mountains . . . And yes, DA can make a huge difference in obstacle clearance. My plane climbs like the proverbial homesick angel solo in January with single-digit-F temps, but is a different animal on a hot July afternoon leaving the beach to come home, loaded as full as my wife can pack.

[gamefreak32]

I'm in a flying club with access to 3 M20Js. Two are pre-1991 (2740 MGTOW) and one is post 1991 (2900 MGTOW). In planning a trip for this weekend, I came across something curious:

 

The 2740 model POH has takeoff performance charts for both "normal" and for "max performance" takeoffs. The 2900 model POH only shows numbers for "normal" takeoff performance. And there doesn't seem to be a reference to an adjustment factor for the later model.

 

Is there a reason for this? Is there a generally-accepted adjustment among experienced Mooney pilots?

Wings of Carolina?

[joneluv]

There is no substitute for cubic inches - Don Garlits?

:-)

[omega708]

There is no substitute for cubic inches - Don Garlits?

:-)

 

I've always heard it as ... "There's no replacement for displacement..."  Although I think the turbo charged guys might disagree. :-)

[midlifeflyer]

Midlife,

I must be misunderstanding your question then...

Are you asking..

Why is there a difference in performance charts between both Js, at identical weights and HP?

That's an interesting question then.

High performance take-offs are another issue. Everything working as the POH requires, including the pilot.

Best regards,

-a-

If you were thinking I was asking about ways to exceed published aircraft limitations, you were definitely misunderstanding the question. My questions were simply:

 

1. Why does the older M20J have charts for both normal and maximum performance (aka short field) takeoffs while the new M20 J has a chart only for a "normal" takeoff?
2. Based upon pilot experience with Mooneys, is there a "short field" takeoff configuration for the later Mooney? If so, what is it and what type of increase in takeoff performance could one anticipate?*

 

The comment about different "normal" performance at equivalent weights between the two versions of the model was more of an observation about the dangers of extrapolation, but yes, it is an interesting question all by itself.

 

(* Aircraft performance charts are not limitations and, especially after flying in the Colorado Rockies for 20 years, I do not consider attempting to determine aircraft performance outside of those charts to be exceeding aircraft limitations)

[midlifeflyer]

Wings of Carolina?

Yes. 

[Carl S]

...

The 2740 model POH has takeoff performance charts for both "normal" and for "max performance" takeoffs. The 2900 model POH only shows numbers for "normal" takeoff performance. And there doesn't seem to be a reference to an adjustment factor for the later model.

 

Is there a reason for this? Is there a generally-accepted adjustment among experienced Mooney pilots?

 

That is interesting.  I have a post 91 model the manual has Normal Takeof Distance and Normal Takeoff Distance -- Grass Surface charts (Sections 5-15 and 5-16).  I would be interested in comparing the differences you mentioned. 

 

My purely speculative W.A.G. as to why there are differences would all point to the company being more consevative in response to the deteriorating legal climate surounding the general aviation industry.

 

I am not sure what you are asking in regard to "accepted adjustment" among experienced Mooney pilots. In my personal experience, test flying one's own aircraft is the best way to determine actual performance and will take into account the test pilot's proficiency and techniques. The FAA Circular 90-89A "Amateur Built Aircraft and Ultralight Flight Testing Handbook" (http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC%2090-89A.pdf) is a trove of useful information if you want to work on something for yourself. This is what I used and still refer to when gathering data for my Long EZ. You could set up a set of tests and perform them in each Aircraft to determine "real world" results and see what differences are noticable.  AC 90-109 might also be helpful as it talks about transition to unfamiliar airplanes but I think the flight testing handbook is what you'd really want.

 

There is a great, and somewhat humorous, series of articles penned by EAA 1000 member Bob Waldmiller.  "The One Hour Flight Test" series contains some math but if you are reading performance tables and finding differences like you did - you can handle it: http://www.eaa1000.av.org/technicl/onehour/onehour.htm

 

A great follow up article is:  Frostbite Falls Flyer Foils Foul Fossil Fueled Fallacy.

 

< edit > Corrected links and added one hour test link. <\ edit>

[Shadrach]

Could you explain Mooney's "high performance" take off procedure?

[Bob - S50]

I'm in a flying club with access to 3 M20Js. Two are pre-1991 (2740 MGTOW) and one is post 1991 (2900 MGTOW). In planning a trip for this weekend, I came across something curious:

 

The 2740 model POH has takeoff performance charts for both "normal" and for "max performance" takeoffs. The 2900 model POH only shows numbers for "normal" takeoff performance. And there doesn't seem to be a reference to an adjustment factor for the later model.

 

Is there a reason for this? Is there a generally-accepted adjustment among experienced Mooney pilots?

 

It might just have to do with marketing.  When our group was trying to find a Mooney to buy I downloaded a POH for a J.  Takeoff and landing data were in the form of graphs that you traced your way through to get your answer.  When we got our '78, the takeoff and landing data was in the form of tables, not graphs.  The graphs allowed you to adjust for tailwind, the tables do not.

 

Also, our '78 POH has no data for descent planning.  Some years do.

 

It may just be what they thought was needed that year.

 

Bob

[kmyfm20s]

Could you explain Mooney's "high performance" take off procedure?

Ignite JATO rocket and pull back on yoke:)

[Carl S]

Ignite JATO rocket and pull back on yoke:)

I believe you are thinking Ercoupe - not 201.

 

http://en.wikipedia.org/wiki/File:First_JATO_assisted_Flight_-_GPN-2000-001538.jpg

[kmyfm20s]

I believe you are thinking Ercoupe - not 201.

 

http://en.wikipedia.org/wiki/File:First_JATO_assisted_Flight_-_GPN-2000-001538.jpg

That's awesome!

[jlunseth]

The "Performance takeoff" was Mooney's term for short field and/or obstacle clearance.  In Section IV Normal Procedures of the POH, you should find procedures for a Normal takeoff and for an Obstacle takeoff.  The Obstacle takeoff procedure is the same as the Normal except for the climb over the obstacle, for which a configuration (probably gear down and takeoff flaps) and an airspeed (slightly more than Best Rate in my aircraft) are specified.  The Obstacle takeoff procedure references a page in Section V Performance, which is the graph for takeoff distance and obstacle clearance (p. 5-17 in my POH), and the Normal takeoff procedure references a different page in Sec. 5, which is the graph for takeoff distance under the Normal procedure.  It is possible that the Obstacle graph assumes a brakes-on-to-full-power takeoff, so the runout may be shorter, not sure about that.  That is how I was taught to do them.

 

Just spent quite a bit of time with these pages, preparing for my Commercial checkride.

[Carl S]

Hmm, looks like it might have been combined into one graph in my manual. Over on the right side there is an obsticle clearance column where the left side gives the lift off performance. Then one follows the line to the right and the 50' clearance distance.

 

[midlifeflyer]

@201_MSE, I don't think that's it. The pre-1991 J POH has two such charts, both showing both liftoff and obstacle numbers. And your still identifies itself as a "Normal Takeoff Distance" chart along the right margin.

[Hondo]

The December issue of the Mooney Flyer discusses a Mooney takeoff accident in which two died.  http://www.themooneyflyer.com/

 

The Mooney POH does not include data for runway slope.  

Cirrus provides the following adjustments:

 

Upslope %   % increase in takeoff distance

1                       22

2                       44

4                       88

 

In this accident they took off with a 2.4 degree upslope.

The wind was calm and a takeoff down slope would have been no problem.

[carusoam]

DP

[Hondo]

Correction, that was a 2.4% upslope, not 2.4 degrees.

[Fry]

Hello all,

I'm pulling up this old thread because I have looked for a explanation for something I do not understand, no matter how long I think about it.

The POH of a 1978 Mooney M20J 201 shows, under "normal takeoff", a ground roll of about 930ft (sea level, 15°C, no wind) . Liftoff speed 63 KIAS. Takeoff weight 2740lbs.

The POH of a 1996 Mooney M20J MSE shows a ground roll of 1500ft. Liftoff speed 59 KIAS. Of course, comparing apples to apples, so takeoff weight 2740lbs, sea level, 15°C, no wind.

That would mean 18 years later, the same engine with the same prop needed about 60% more distance to accelerate the same mass to even a lower liftoff speed.

That makes no sense to me. Can you resolve this puzzle? Which POH is right? What are your real-world ground roll distances?

I am asking because I am contemplating the purchase of a 1995 M20J MSE and I'm based at a paved 1800ft strip.

Thanks!

 

Edited July 3, 2019 by Fry