M20J vs M20J Takeoff Performance

[Urs_Wildermuth]

On ‎7‎/‎3‎/‎2019 at 4:10 PM, mooneyflyfast said:

You didn't ask for advice on the advisability of basing an M20J on an 1,800 foot strip but I am going to give it to you anyway FWIW.

In Europe you will find tons of Mooneys on 1500 ft runways or less, primarily because lots of airfields are that small yet Mooneys are popular and operate in and out of there without any problems.

Wangen Lachen (LSPV) has a 500x18m runway, which translates into 1640 ft. I've been there many times, no problem either in or out. There are quite a few Mooneys based there including a M22 Mustang and an Eagle which belongs to the local flying group. I've seen J, K's and others there.

The original Mooney dealership in Switzerland was based in Bad Ragaz LSZE. Its runway is 1624 m long and 33 ft wide. For many years all Mooneys coming into Switzerland for sale (quite a few) passed through there.

Shortest I know of that my airplane has operated in and out of was Helgoland in Germany, whose longest runway is 1570 ft long. It did operate out of there with 3 POB.

The simple thing is: Open the POH and see what it can do. Take Off is rarely the problem, landing on short runways you have to get it right of course. But I would not hesitate to take my C model into 1600 ft provided there are no other factors like obstacles or else which make it a problem.

I could not really make out the differences in those pictures due to quality. But there must be a quite fundamental change between the two which I am convinced has to do with a change in conditions or in the way calcs were done unless really a massive change in the construction has occurred which I believe it has not.

Unfortunately Mike Miles is no longer with us, he would have known for sure. Maybe Bob Kromer can be found somewhere? He might have an idea.

[carusoam]

On 7/3/2019 at 4:12 PM, jaylw314 said:

So a hypothesis on what might play a role here is that the FAA defined "takeoff distance" as 1.15x the distance required to reach a height of 35'.  That definition only has to do with aircraft certified under part 23, which does NOT apply to M20's, but I wonder if Mooney started using that definition at some point in the last 20 years?  Anybody know?

Hmmm...

I’ve seen a pilot to have reported reaching 35’ in a take-off accident report recently, where the video showed something more like three or five feet...

You might think that pilot may have known more than what he had actually demonstrated...?

 

It is interesting that the FAA has implied a fudge factor to the data before the pilot does the same...

Why would the FAA apply this particular 1.15 and 35’ fudge factor on top of real data?

Would that somehow cover variations in plane manufacturing and height of chain link airport perimeter fences?

There has got to be some interesting detail there.

Best regards,

-a-

 

Jay, where’d ya go?

Looks like the title just changed... wasn’t it a J vs. K discussion?

Funny bug seems to have occurred... again.

[mooneyflyfast]

Having unlimited clear approaches and overruns like those pictured in Europe would make a big difference--we don't have many (any?) like that around here.  While my airport (1t8) has 2,890 feet of pavement, on the north end within 20-30 feet of the end of the runway there is a pole line, a barbed wire fence and a road.  rwy 16 has a 420' displaced threshold.  On the south end there are trees, a 6" concrete curb and an 8' dropoff at the end of the pavement. Rwy 34 has a 200' displaced threshold.  

The most challenging airport I know of around here is Twin Oaks (T94).  It has 2,225 ' of pavement but the approach to 12 has trees, a fence and a street. The runway is sanwiched into a residential neighborhood about 2 miles north of San Antonio international.  There is a wooden fence 70' from the runway. Rwy 30 has trees at the approach end. Rwy. 12 is downhill so the people I know who base there (2, a 210 and a 206) will accept up to a 10 knot tailwind for landing on 30). Prevailing wind is SE here. One of the most experienced pilots I know (pro pilot, Gulfstream corporate, etc) lives there and flew a beautiful J model Mooney a couple of serial numbers from mine.  A year or two ago he made the local news by landing on 30 and running thru the fence at the end coming to rest in the street.

[Urs_Wildermuth]

1 hour ago, mooneyflyfast said:

Having unlimited clear approaches and overruns like those pictured in Europe would make a big difference

They are not that unlimted, the first airfield, if you land from the east there is a water canal at the runway end. But in all the time I've flown my Mooney there I never needed more than up to the first taxiway, that is about 300m. Helgoland, the lowest one, has earth walls and soft ground on the respective sides.

Almost no runway in Switzerland for small aviation is above 3000 ft, most are between 1500 and 2000 ft. We grow up with those so we don't consider them particular.

Even on large airports we are expected to land short and get the heck out of the runway to make space for the big guys.... Consequently at ZRH many years ago a crew took the landing clearance to leave at the first taxiway to the left too literally and did a 300 ft ground roll with smoking brakes, turned into the very first taxiway directly into the face of the airliner waiting to line up. That crew on that DC9 had a great laugh until the GA plane lost pressure on both tires and had to be recovered. The actual taxiway they were supposed to use was about 500m down the runway.

 

[midlifeflyer]

Like other threads if this type, there is a lot of dichotomy between the capability of the airplane and the abilities and comfort level of the pilot.

It's not really a Mooney issue. I get into discussions with friends about going places. They will express concerns about going into airports where I wouldn't hesitate. In many of those it's not about my friend's abilities as much as our differing types of experiences.

 

[midlifeflyer]

10 hours ago, carusoam said:

 

Looks like the title just changed... wasn’t it a J vs. K discussion?

 

Nope. Havig started it 5 years ago, it was about performance char differences in different generation J's.

[gsxrpilot]

7 hours ago, midlifeflyer said:

Like other threads if this type, there is a lot of dichotomy between the capability of the airplane and the abilities and comfort level of the pilot.

It's not really a Mooney issue. I get into discussions with friends about going places. They will express concerns about going into airports where I wouldn't hesitate. In many of those it's not about my friend's abilities as much as our differing types of experiences.

 

Truth.

[PT20J]

On 7/3/2019 at 4:50 PM, PT20J said:

Here are the pertinent pages from the POH/AFM for my '94 J (TOP) and my '78 J (BOTTOM). The newer version doesn't specifically say "ground roll" but that can be inferred by an obstacle height of 0'. For 20-deg C at sea level and 2740 lbs. the '78 version shows a ground roll of 965' and 1831' over the 50' obstacle whereas the -94 version shows a ground roll of 1440' and 2200' over a 50' obstacle. That's a whopping 49% increase in ground roll and a 20% increase in distance to clear a 50' obstacle. All the listed test conditions are the same except that the '78 version notes to lean for smooth operation (which shouldn't make a difference at sea level) and the '94 version references 80% relative humidity. Using an online calculator (https://wahiduddin.net/calc/calc_da.htm), 29.92 in-Hg, 20 deg-C, 80% RH is a DA of 826' whereas the same conditions at 50% RH yields a DA of 737' -- hardly significant. The stated liftoff speeds are about 5 KIAS lower for the later version which I would expect to decrease the ground roll all else being equal. Maybe @mike_elliott or @donkaye or one of the other Mooney instructors has an explanation. 

Skip

 

 

 

 

So where are all the MAPA PPP instructors? I thought you’d be all over this with an explanation by now. With all the pilots flying different year Js attending the classes over the years, this can’t be the first time this has ever been noticed, can it?

[kortopates]

23 minutes ago, PT20J said:

So where are all the MAPA PPP instructors? I thought you’d be all over this with an explanation by now. With all the pilots flying different year Js attending the classes over the years, this can’t be the first time this has ever been noticed, can it?

Certainly can't speak for all MAPA instructors but when discussing performance, the emphasis across all models has been in the IFR numbers for different IFR PAC as in flying IFR by the numbers. That's not to say an example plane wasn't used to review deriving performance numbers for takeoff and landings, but that sort of thing isn't discussed across all models like the PAC's used for IFR. The closest thing that gets discussed across the many different J's is the max gross weight differences and eligibility requirements for it. 

I'd suggest reaching out to Frank Crawford at Mooney, since he is responsible for maintaining all the documentation including POH's and Maintenance manuals. If you PM me, I'll share his email address.

Edited July 6, 2019 by kortopates

[PT20J]

1 hour ago, kortopates said:

Certainly can't speak for all MAPA instructors but when discussing performance, the emphasis across all models has been in the IFR numbers for different IFR PAC as in flying IFR by the numbers. That's not to say an example plane wasn't used to review deriving performance numbers for takeoff and landings, but that sort of thing isn't discussed across all models like the PAC's used for IFR. The closest thing that gets discussed across the many different J's is the max gross weight differences and eligibility requirements for it. 

I'd suggest reaching out to Frank Crawford at Mooney, since he is responsible for maintaining all the documentation including POH's and Maintenance manuals. If you PM me, I'll share his email address.

I've got Frank's contact info and I'll try to chase it down at Mooney. But, still...

[mike_elliott]

4 hours ago, PT20J said:

I've got Frank's contact info and I'll try to chase it down at Mooney. But, still...

Skip, to ask a Mooney CFI to explain why Mooney test data and performance charts are different between the 2 years of J's in your example would be non authoritative unless of course that Mooney CFI was the author of the data tests. Frank may be able to provide the answer, but it might be better to have him guide you to the specific test pilots who conducted the test for both. Perhaps Bob Kromer could shed some light on the latter

[M016576]

On 7/4/2019 at 11:40 AM, Urs_Wildermuth said:

There are quite a few Mooneys based there including a M22 Mustang and an Eagle which belongs to the local flying group. I've seen J, K's and others there.

That’s where all the M22’s went!!! Europe!!! One to fly, and the other 20 for parts!