Oops, Botched the First Landing | The VSKYLABS Support Forum

longezdreamer
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Flying LongEZ and Cabri G2

Posts: 39

Oops, Botched the First Landing Nov 27, 2018 2:35:05 GMT

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Post by longezdreamer on Nov 27, 2018 2:35:05 GMT

I usually pattern "my EZ" at 80, final at 70KIAS with half speed-brake and dump the power at or a little before threshold to land at 60-65. This is a little faster than the POH recommends (pattern at 70-75, final at 65, touchdown at 55 knots).

For my first pattern, (no wind), I trimmed on downwind (with half speed-brake) to 80KIAS like my usual. It seemed like the vSkyLabs EZ needed more power than "my EZ" (Lycoming 235 115hp). I usually pattern at 1750-1850rpm. For the vSkyLabs EZ, I had to keep the rpms above 2000 to hold altitude.

On final I trimmed to 70 (still with half speed-brake). It still seemed to want 2000rpm to hold the descent rate right.

As I crossed the threshold (40-50 ft AGL) and dumped the power, the nose dropped very quickly. Airspeed stayed at 65, as I pulled back increasingly aggressive to try and bring the nose up. At impact the nose wheel collapsed, the airspeed indicated 65, VSI at -1000, rpm 1000, and the stick was full back. I skidded to a stop on the collapsed nose.

It seemed to just fall out from under me.

From the POH: "The Long-EZ has good flight characteristics at minimum speed. It is a docile, controllable airplane at full aft stick at it’s minimum airspeed of 50 to 55 knots. It doesn’t exhibit any of the conventional airplane’s tendencies to roll, pitch down uncontrollably or other common un- commanded flight path excursions."

The LongEZ is known for its long landing if you're fast.

Is anyone greasing the landings at the POH speeds?

Last Edit: Nov 27, 2018 5:26:28 GMT by longezdreamer

LongEzDreamer

longezdreamer
New Member

Flying LongEZ and Cabri G2

Posts: 39

Oops, Botched the First Landing Nov 27, 2018 5:16:38 GMT

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Post by longezdreamer on Nov 27, 2018 5:16:38 GMT

(Disclaimer: I do not know if x-plane Planemaker Airspeed Limits actually affect the simulation.
I am only trying to figure out possible explanations for why I couldn't flare at 65 knots.)

Is there a reason the stall speed on the VSKYLABs LongEZ is set to 65 knots?

Here is the planemaker Vspeeds for the VSkyLabs LongEZ on the left and "my LongEz" on the right:

The flight model of "My LongEZ" comes from:

vezePilot's LongEz O-235

which was tuned by vezePilot (a Velocity owner) to match his friend's LongEz flight characteristics. Note the 49 and 52 knot Vso and Vs stall speeds would seem a better choice to match the POH than 65 knots, no?

=== Noticing another difference - Vno=120. This would not have affected my landing. ===

The POH on V normal operation Vno:

CRUISE
Maximum recommended cruise power setting is 75%. A high cruise power setting (full throttle at 8000 ft density altitude) will result in the maximum true cruise speed of 161 knots (185 mph) for Lycoming and 149 knots (171 mph) for Continental.

Does it matter that the VSkyLabs Vno is set to 120?

Last Edit: Nov 27, 2018 5:22:58 GMT by longezdreamer: combined vspeed graphics for easier comparison

LongEzDreamer

VSL-Admin
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Posts: 931

Oops, Botched the First Landing Nov 27, 2018 8:20:54 GMT longezdreamer likes this

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Post by VSL-Admin on Nov 27, 2018 8:20:54 GMT

Hi

OK...

Lets begin with general speeds and limitations:

As in real-life...every home-built is different than other...depending on its owner's/builder's approach and specifications selected when built (engine selection, propeller selection, materials used, overall weight...canards selection etc...).

So...comparing the VSKYLABS LongEZ, which was built as a 'home-built' project, but to follow the design specs of the NR79RA prototype, with another one, may show a few differences in performance and handling.

Now for some practical aspects:

First, check on your weight (payload and fuel) settings. You will find out that depending on that, with an aircraft flying a single pilot and 25%-50% fuel load, the stated docile flying handling at airspeeds of around 55 knots is possible without special issues. Give it a try, it will affect the landing handling dramatically, and you will be able to flare at 55 knots easily.

The original user manual for the LongEZ is introducing the design values which were used for the VSKYLABS LongEZ. Rotation speed is 50-60 knots (depending on CG), while liftoff should be executed around 65-70 knots. The VSKYLABS LongEZ is following these specs with reasonable margins.

Landing, according to the original manual should be carried with pattern speed of 70-75 knots, slowing to 65 knots on final. Touching down at 55-50 knots is straight forward, but again, depending on your fuel and weight configuration.

As for the values in Plane maker:
Please note that these (stall speeds etc...) are not affecting the flight dynamics model and will not determine whenever the plane will stall. It is for reference only. Try it yourself; set the plane with different weight and fuel loading configuration and see that you can skim along at ~52 knots without stalling.

I am familiar with the vezePilot LongEZ (there is also a link to his website and project, in the VSKYLABS LongEZ page, along with a recommendation of being a very interesting resource of freeware, good quality models for X-Plane - look for it at the bottom of the VSKYLABS project page: www.vskylabs.com/2018/04/vskylabs-rutan-longez-project.html?m=1 ).

So, in general, these two LongEZ (VSKYLABS, vezePilot) are representing the same aircraft but with slightly different configurations (engine, props and other aspects). My approach on this is like as it is in real life...two different home-builts of the same plane, which were built with different specs, will show some differences. Although not too much of a difference as it is a LongEZ after all..

Regarding the botched landing

...try to start these landing trials with a light aircraft configuration (25% fuel, low payload), and gradually learn how it behaves.

It is important to say that the project is under constant development, and seeking for the most accurate flight dynamics and handling characteristics is an ongoing, continuous effort. Every user feedback and inputs are taken into account, being analyzed and if needed, they are implemented.

Here is a short video of some landing-tests runs which were made a while ago...trying (with success) to land with the nose wheel retracted...holding it up while being extracted, all together in the ~60 knots speed range. This was done with latest version v1.4 at ~60 knots, 50% fuel.

(video is a bit of a low quality...)

Last Edit: Nov 27, 2018 8:23:01 GMT by VSL-Admin

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longezdreamer
New Member

Flying LongEZ and Cabri G2

Posts: 39

Oops, Botched the First Landing Nov 27, 2018 13:58:47 GMT

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Post by longezdreamer on Nov 27, 2018 13:58:47 GMT

Nov 27, 2018 8:20:54 GMT VSL-Admin said:

Regarding the botched landing

...try to start these landing trials with a light aircraft configuration (25% fuel, low payload), and gradually learn how it behaves.

...check on your weight (payload and fuel) settings. You will find out that depending on that, with an aircraft flying a single pilot and 25%-50% fuel load, the stated docile flying handling at airspeeds of around 55 knots is possible without special issues. Give it a try, it will affect the landing handling dramatically, and you will be able to flare at 55 knots easily.

I stand accused of doing a "John Denver" with luck to have a "Chuck Yeager Landing". I did an hour of cockpit familiarization, set payload weight to my 190 lbs of "beer belly", and left fuel at the default four hours load. At the very least, I deserved the embarrassment of a bad landing for ignoring the "First Flights" section of the POH. (When I got my first Ez, I did all the taxi tests and listened to the guidance. This time, I let my excitement rush things. (It is exactly this kind of thinking that led me to let my private pilot license lapse non-current 20 years ago, and only fly the "safe skies of flight simulation.")

As for the values in Plane maker:
Please note that these (stall speeds etc...) are not affecting the flight dynamics model and will not determine whenever the plane will stall. It is for reference only

Great to know. Thanks.

... short video of some landing-tests ... land with the nose wheel retracted...holding it up while being extracted, all together in the ~60 knots speed range. This was done with latest version v1.4 at ~60 knots, 50% fuel.

WOW - THAT IS SO AWESOME!

From my home base at KLNA Lantana, Florida, USA, there is a grass field that I like to fly to. The flight takes me directly over my house, which just happens to get modeled quite accurately in the auto-gen scenery. Having read the strongly cautions about operations on grass in the POH, I always try for a minimum speed mains landing, holding the nose up. The sudden drag on the mains usually jerks the nose wheel to the turf but it has never collapsed on me before.

I stand in awe of the video landing! That's some flyin'

LongEzDreamer

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Oops, Botched the First Landing Nov 28, 2018 6:39:47 GMT longezdreamer likes this

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Post by VSL-Admin on Nov 28, 2018 6:39:47 GMT

Thanks!

btw...this nose-high gear-retraction procedure is documented in the original user manual:

(quote):
LANDING GEAR EMERGENCIES

Since only the nose gear retracts, and it’s actuation system is so sim-
ple, failure to extend or retract properly is highly unlikely. A far more

likely failure is the pilot forgetting to extend the gear. Should you find
yourself in the landing flare or even rolling along on the mains at 50
knots or more, you can easily hold the nose off to make a go around
or even extend the gear at that point. If you just can’t avoid landing
gear up, hold the nose off for as long (and slow) as practical, then fly
the nose gently to the runway. Avoid nose- high canard stall and the
nose dropping hard to the runway.

So this demonstration/test is one of the items which needs to be plausible to reproduce with the simulation model.

Last Edit: Nov 28, 2018 6:40:18 GMT by VSL-Admin

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n56yc
New Member

Posts: 9

Oops, Botched the First Landing Sept 18, 2020 1:35:14 GMT

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Post by n56yc on Sept 18, 2020 1:35:14 GMT

Reading LongEzDreamer’s first comments about carefully controlling speeds in the landing sequence, the high RPM needed to keep the AC from stalling, and his remark of “it seemed to just fall out from under me” when flaring, I have to agree. My landings have gotten better but I’m still struggling with it after dozens of landings. I’ve been blaming this on having trained in real life in a Cessna which has a tendency to float and on not being able to more readily adapt to the differences. Landing and stall speeds are fairly similar in a clean configuration (no flaps), so I would have expected those landing characteristics to be more or less the same. I’ve not yet tried a lighter configuration, having always flown with tanks at least 3/4 full. The videos here illustrate the degree of fine control that is possible, but when it comes to landings it’s a challenging bird to master.

Last Edit: Sept 18, 2020 1:40:03 GMT by n56yc

n56yc
New Member

Posts: 9

Oops, Botched the First Landing Sept 19, 2020 5:35:00 GMT

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Post by n56yc on Sept 19, 2020 5:35:00 GMT

After reading the EZ POH again I saw the discussion re. landing technique that I had previously overlooked. The handbook says that the flare should be complete but brief and the airplane landed as soon as possible. This is very different than in a Cessna where you would hold off in the flare with the airplane just barely above the ground for as long as possible to bleed off speed, you keep pulling back on the yoke smoothly and continuously until the stall horn goes off and a fraction of a second later the airplane touches down. This technique obviously doesn't work for the EZ, so it takes some getting used to.