Flight Modeling/Landing

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vati1werner
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Joined: 09 Sep 2006, 21:12

Flight Modeling/Landing

Post by vati1werner » 14 Sep 2006, 18:55

Is it me or is this thing hard to coax to the ground? When I flare at what appears to be just above (or even at stall speed) this thing will float back up again and feels like it could climb back into the sky and won't touchdown without serious forward pressure on the stick. This may be how the real plane handles but I've never had the pleasure. This may have already been addressed but I haven't seen a posting for it. Another small issue is that the ground roll sound doesn't seem fully synched with the speed of the craft while rolling. It sounds like the tires are rolling at 15 kts or so when the plane is only crawling. Thanks.

snave
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Post by snave » 14 Sep 2006, 19:57

It's called ground effect and is exactly what I've been waiting for from a flight model for years. Touchy, but rewarding if flown right.

I haven't flown a Safir, but I do have over 800 hours in high and low-wing aircraft and they all have some kind of quirk when close to or on the ground.

Generally, low-wing aircraft will `float` in ground effect even if only 4-5kts above the correct landing speed, which may or may not equate to what the ASI is telling you at that point, as they lie at low airspeeds too!

You need to go back and fly an accurate approach, dropping the IAS until you get the contact point where you want it more or less consistently. And then use that speed for that weight. Always.

Suggest using a long runway, unaffected by traffic. Set up a flight so that you are already on short finals, save it so you can restart from that point and just fly, fly and fly that final approach again and again!

....Oh and Ssshh! The other main reason for floating is you're landing downwind... We've all done it. Just to practice you understand.... :oops:
Simon Evans

vati1werner
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Post by vati1werner » 14 Sep 2006, 20:23

Snave, thanks for the insight. Wasn't sure if that modeling was deliberate, my inexperience, or both.

snave
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Post by snave » 15 Sep 2006, 14:58

The model was tested by Safir owners, and has been commented on for its accuracy. I love it!

It seems that the split flaps add more lift than drag and have quite a pitch trim change when operated - this was common in older aircraft when flaps were essentially little more than airbrakes and given the Safir's age, entirely in keeping with its design heritage.
Here's a summary of the different types of flap
http://selair.selkirk.bc.ca/aerodynamic ... html#split

But, those flaps ain't all that big, (probably just as well as they'd drag on the ground on anything other than tarmac if they did!) so all I do is add a little sideslip as needed to increase the rate of descent or check the speed while on short finals. That certainly works, whether or not it's SOP in the real thing! Landing speed is 100km/h or about 54 knots so I'd use that as your starting point for experimentation and slowly drop it to about 49 or even 48 knots/90 kmh until you find the speed at which you can make that consistent touchdown point.

Perhaps a real Safir flyer could chime in with some more detailed pilotage info?
Simon Evans

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pj_3
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Floating. .

Post by pj_3 » 15 Sep 2006, 17:28

. . .having a coupla hundred hours in the old DH Chipmunk in the RAF - I will guarantee that - if you don't get the airspeed down where it needs to be - you are going to float a foot off the runway forever! I noticed it on the first landing, and it was so good - maybe a first - to finally find an model which portrays this.
Paul J

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Voyager30
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Post by Voyager30 » 15 Sep 2006, 17:59

:-D :-D :-D :-D
....Oh and Ssshh! The other main reason for floating is you're landing downwind... We've all done it. Just to practice you understand....
indeed.. you will remember it after yo uhave done it :lol:

snave
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Post by snave » 15 Sep 2006, 21:42

Voyager30 wrote::-D :-D :-D :-D
....Oh and Ssshh! The other main reason for floating is you're landing downwind... We've all done it. Just to practice you understand....
indeed.. you will remember it after yo uhave done it :lol:
Usually when someone points at the windsock, leaving you only a brief window of opportunity to reply: "Yes I saw that on joining the circuit, but thought it might be a good day to practice a downwind..." :D

Will fool most passengers, but not most pilots, I find. :oops:
Simon Evans

vati1werner
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Post by vati1werner » 16 Sep 2006, 04:38

I've been trying to master landing; doing quite a few touch and go's. I'm starting to get the hang of this bird and it's a blast! Thanks for the tips.

snave
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Post by snave » 16 Sep 2006, 15:28

vati1werner wrote:I've been trying to master landing; doing quite a few touch and go's. I'm starting to get the hang of this bird and it's a blast! Thanks for the tips.
Our pleasure. It really is a remarkable flight model, well up there with the best ever... :wink:
Simon Evans

jantar
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Post by jantar » 19 Sep 2006, 09:19

When flying the real Safir you have to land it nearly like a taildragger. I fly the circuit at 150km/h dropping to 135 on final, slowly cut the throttle over the threshold and then just keep easing the stick back until she settles on the runway. You don't really have any forward vision over the nose cowling. She does use quite a lot of runway, I saw someone here saying she'd make a great bushplane, I'm a bit sceptical about that. On the other hand I don't think I have ever made a lousy bouncing landing in the Safir. I suppose that is much due to the ground effect discussed above. I have experienced a flat tire on the left main gear while taxying in after landing, and I tell you that's not fun at all in a plane with a castoring nose wheel. :(
/J

snave
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Post by snave » 19 Sep 2006, 15:44

jantar wrote:When flying the real Safir you have to land it nearly like a taildragger. I fly the circuit at 150km/h dropping to 135 on final, slowly cut the throttle over the threshold and then just keep easing the stick back until she settles on the runway. You don't really have any forward vision over the nose cowling. She does use quite a lot of runway, I saw someone here saying she'd make a great bushplane, I'm a bit sceptical about that. On the other hand I don't think I have ever made a lousy bouncing landing in the Safir. I suppose that is much due to the ground effect discussed above. I have experienced a flat tire on the left main gear while taxying in after landing, and I tell you that's not fun at all in a plane with a castoring nose wheel. :(
/J
How interesting! That is exactly how I've taken to landing the FS Safir! Carry a little power past the threshold, raise the nose until you can hardly see the runway, then pull of the remaining power and look out the side to `feel` for the ground.

Thanks for the info! :lol:
Simon Evans

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Hakan_Olsson
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Post by Hakan_Olsson » 19 Sep 2006, 18:33

jantar wrote:She does use quite a lot of runway, I saw someone here saying she'd make a great bushplane, I'm a bit sceptical about that.
I'm not sceptical at all. The Safir's take off performance isn't anything to write home about.
It's very reluctant to leave the ground compared to a lot of other light singles. But when you picked up some speed it really comes into it's own.

One reason why it's possible to perform nice aerobatics in it is because it handles so nicely when stalled. You have full control over the aircraft even with a lot of buffeting.
In fact I belive the Safir has a better roll rate at taxiing speed than a Cessna 172 has at cruise speed. :D

Best regards,
Håkan
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snave
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Post by snave » 19 Sep 2006, 20:25

ROFLMAO! :-D

A slug under anaesthetic performing a slow roll while stapled to a table which has been set in a 2-ton concrete slab has a better roll rate than many of the 172's I've piloted. :evil:

As an experiment I removed all the null zone from the Safir control responses using FSUIPC registered version and checking them for that aircraft only (you have to do it for each model in turn).
Fantastic feel, and the only aircraft in my collection - which includes many, many flight models from the so-called `greats` - that actually handles even better from doing that... :D :-D :D :-D
Simon Evans

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Hakan_Olsson
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Post by Hakan_Olsson » 19 Sep 2006, 21:51

snave wrote:ROFLMAO! :-D

A slug under anaesthetic performing a slow roll while stapled to a table which has been set in a 2-ton concrete slab has a better roll rate than many of the 172's I've piloted. :evil:

As an experiment I removed all the null zone from the Safir control responses using FSUIPC registered version and checking them for that aircraft only (you have to do it for each model in turn).
Fantastic feel, and the only aircraft in my collection - which includes many, many flight models from the so-called `greats` - that actually handles even better from doing that... :D :-D :D :-D
Simon,

Due to the softly sprung gear and narrow track in combination with very effective ailerons it is possible to waggle the wings quite noticeably at normal taxi speed which can hardly be said about the 172 :D

The Safir in real life has no null zones at all and the stick forces are very light so I belive this flight model gives a new dimension to "reality" in the FS community. What I mean is that the control forces of my Logitech joystick matches the Safir perfectly !

I must confess that flying the Safir was a sort of 'wet dream', in aviation terms, for me for many years. When the dream finally came true it was well worth waiting for ! :D :D :D

Best regards,
Håkan
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