Basic flying

[SE-HK]

Hi!

I have read http://flightgear.org/Docs/getstart/getstartch7.htm but have some questions regarding basic flying of the Cessna. First at take-off:
Is it correct that I should give full throttle and then let the speed be 70-75 knots and correct it by using the yoke? I am wondering since I read somewhere that a good climb rate was 600 ft/min, now it's over 1000 ft/min.

Next is about cruising. Which is the usual height to fly (in real life) in case we are above land at sea-level? Is it 3500 ft?
What is ideal crusing speed, is it still 75 knots? Should I use throttle, yoke and trim to keep same speed without elevating?
I am wondering since I feel my plane is not aligned aero-dynamically good, also I thought the horizon is to low, please see "photo" below:

cruise2.png

cruise4.jpg

Perhaps I need to trim it down?

[flameout]

I am not an actual pilot, but here are my answers (to the best of my knowledge) to your questions:

Is it correct that I should give full throttle and then let the speed be 70-75 knots and correct it by using the yoke?

You should begin rotating (lifting up) at 55 knots, and it will be more like 60-65 knots when you actually leave the ground. Then climb at a shallow rate to accelerate to 70-75 knots and then correct your speed with the yoke. Climb out at full throttle, and control the airspeed with the yoke. So yes, at least on climbout, you hold your speed with the yoke.

I am wondering since I read somewhere that a good climb rate was 600 ft/min, now it's over 1000 ft/min.

I would guess that the 600 ft/min would be for climbs at higher speeds, past the initial climbout. Over 1000ft/min is fine when you are just leaving the airport and trying to build a safe margin from the terrain.

Next is about cruising. Which is the usual height to fly (in real life) in case we are above land at sea-level? Is it 3500 ft?

As far as I know, there is no one cruise height. Longer flights generally have higher cruise levels, but the terrain also affects it. If you take off from an airport at 9,000 ft (there are some, but I forgot any names I knew,) your cruise will (hopefully obviously) not be at 3,500 ft.

What is ideal crusing speed, is it still 75 knots? Should I use throttle, yoke and trim to keep same speed without elevating?

It is higher than 75 knots, as far as I know. Personally, although this is probably a little higher than a realistic speed (fuel is free in FlightGear,) I just fly at full throttle at cruise. However, you'd have to look up the cruise speed (or have someone more knowledgeable respond) to know it for sure. It's probably at least 120 knots.

I hope this helps, and enjoy FlightGear.

[FlugHund]

I am wondering since I feel my plane is not aligned aero-dynamically good, also I thought the horizon is to low, ...

Your feelings are correct here, but: look at the plane when it is on the runway. You'll see that the wheels are not on the ground and the 3D model is not at level. Which means the fdm and the 3D model are not aligned and therefore even if one fly correct the displayed model crooks in the air.

I think this situation was caused by a discussion without solution on devel list. I bet the author of the new c172p 3D model knows some more details about this... (HHS, your turn )

Alex

[sim]

Hello SE-HK,
The 70-75 Knots you quote is climb speed to get to whatever cruise altitude you need. As Flameout says cruise altitude depends on the height of the terrain on your chosen route.This altitude may change on route as maybe you have mountains ahead of you or a city where the local Air Traffic Controller will give radio instructions to divert you safely around, over or under danger zones or other air traffic. it also depends on your pilot rating, you won't be qualified to fly IFR (Instrument Flying Rules) until you have lots of experience and have passed a test to gain a IFR rated licence involving blind flying using your instruments and nav aids.
For now you can assume you fly only under VFR (Visual FR) conditions where you are confident you can see where you are going and what obstacles may lie ahead. Even without a radio you carry maps showing airfields on route, no go danger zones, restricted airspace or airways crossing your route where for example you keep below 3000' under the airway or over 10,000' to keep above its upper limit. Apart from that keep your eyes peeled and the world's your oyster.
Cruising altitude reached now? The plane will find its own airspeed holding that altitude, so check your altimeter remains at 2500' say and your rate of climb indicator needle remains horizontal. You can relax your grip on the stick a little if you set elevator trim so the plane's airspeed settles at a constant speed and height remains 2500'. Don't get mesmerized constantly head down watching these instruments! Enough to glance now and again.
Your nose will maintain a constant position in relation to the horizon, it may be this position is different because today you have chosen another plane to fly, remember that position for next time you fly it! Just adopt that position because mostly you should be watching where you are going and there is no conflicting traffic left or right. You can do any fine trim adjustments glancing at ASI and Altimeter as you go along. You'll fly a lot better if you relax and enjoy the landscape and skies you pass through on your travels.
Enjoy, sim

[HHS]

...I think this situation was caused by a discussion without solution on devel list. I bet the author of the new c172p 3D model knows some more details about this... (HHS, your turn )

Alex

Yep, there was a discussion on a (possible?) wrong alignement of the new 3d-model I made. It is still not solved.
The problem is that the c172p has a tail-hangdown attidude on ground with empty weight:http://www.airliners.net/photo/Untitled-TC-Air/Cessna-172M-Skyhawk/1572934/M/
But with cruise speed it should be much more leveld with horizon.

For me it is much more difficult to get a JSBsim-model aligned than a YASim-model.
I hope to get a solution soon, so the next FGFS-release will have this issue fixed.

[SE-HK]

Thank you all for your responses!

When I first started to use FG some 1.5 or 2 years ago I just flew it. After a break I started flying again and thought I would do it a little bit more realistic so I've read parts of chapter 7 of the manual a few times while flying. But new questions came up so I registered on the forum.

It always says "use rudder close to ground" instead of yaw. Where is close to ground? Is it 25, 100, 500 or 1000 ft?

Now I will start flying more with feeling but still I am under VFR!

[AndersG]

For me it is much more difficult to get a JSBsim-model aligned than a YASim-model.
I hope to get a solution soon, so the next FGFS-release will have this issue fixed.

Why? You determine where the origin of the FDM coordinate system is and its alignment, hopefully by it being documented in the FDM config but otherwise by looking at e.g. the gear, engine and propeller positions and working backwards from there. Then you look at the 3d model and determine its coordinate system. If they are axis aligned you only need to set appropriate offsets in the 3d model XML file or even easier by setting the VRP in the FDM config to coincide with the 3d model origin.
If the two coordinate systems are not axis aligned you will need to use rotational offsets in the 3d model XML file, which will make the definitions of animations and view positioning complicated (my advice would be to rather change the 3d model to avoid that). This case would be equally difficult with YASim.

Given that the c172p FDM config doesn't document its coordinate system origin and alignment and on top of that is measured in inches I can see why you find it a pain to work with, though. OTOH that isn't an inherent flaw in JSBSim. :)

/Anders

[HHS]

If the two coordinate systems are not axis aligned you will need to use rotational offsets in the 3d model XML file, which will make the definitions of animations and view positioning complicated (my advice would be to rather change the 3d model to avoid that). This case would be equally difficult with YASim.

Given that the c172p FDM config doesn't document its coordinate system origin and alignment and on top of that is measured in inches I can see why you find it a pain to work with, though. OTOH that isn't an inherent flaw in JSBSim.

/Anders

Changing the 3d-model is very time consuming regarding positioning instruments.
And yes, the fdm config is a pain, because it is much more difficult to get coordinates then yasim.

[AndersG]

Changing the 3d-model is very time consuming regarding positioning instruments.
And yes, the fdm config is a pain, because it is much more difficult to get coordinates then yasim.

If the orientation differs between the 3d model and the FDM I don't think you have any other choice[*] than rotating the 3d model to correct it (no matter if you use YASim or JSBSim). However, to reduce the consequences, perhaps you could put the entire instrument panel and other complex parts in separate XML files and load these as models - then you only need to correct for the new 3d model coordinate system in the few <model> elements that load these files instead of in the <model> element of each instrument.

[*] Short of rewriting the FDM for a differently aligned coordinate system.

/Anders

[HHS]

.....However, to reduce the consequences, perhaps you could put the entire instrument panel and other complex parts in separate XML files and load these as models - then you only need to correct for the new 3d model coordinate system in the few <model> elements that load these files instead of in the <model> element of each instrument....
/Anders

Yep- that sounds like a good idea to solve this issue.
I will see what I can do - I will go one with the c172p the next time and see how big the difference will be....

[sim]

Hi HHS,
Using Rudder: Use your rudder on the ground during take off to counter any tendancy to swing left or right due to engine torque, X-wind etc. As you gather speed generally you can ease off the big bootful you needed initially. Just aim to keep straight down the runway centreline. You may also find with tailwheel planes a short tendancy to swing off course at a higher speed as the tailwheel lifts. Sometimes you can prevent this by keeping the stick held back in your guts but watch out when you get flying speed as you will leap into the air and need to push forward pretty sharply to get level!
Otherwise rudder use won't bother you until later when you need to practice crosswind landings. The secret here is the runway is coming at you from an angle, it may be to your left or to your right according to which side the wind is blowing, just boot the rudder to straighten the plane so it heads down the centreline just before touchdown. Don't hang about, your wheels need contact with the deck shortly after or the wind will start you drifting again and you may have to abort landing.
Good practice for X-wind landing, without a wind is an old skill oft neglected that old biplane pilots learnt early on -> The sideslip approach, where you need to increase your rate of descent to put down in a small field over tall trees, bang on full rudder at the top of your approach, say full right rudder, then hold your left wing down enough to set your direction of travel down the runway centreline, bearing in mind your nose will be way off to the right! Same technique straighten up just before landing. The beauty of this practice is there ain't no cross wind so it's not so urgent to make this adjustment in the last seconds before your wheels ground!
Cheers, sim

[sim]

SE-HK,
Your question way back last Sept

It always says "use rudder close to ground" instead of yaw. Where is close to ground? Is it 25, 100, 500 or 1000 ft?

The answer is 25ft might be ok for a big airliner but on light aircraft it may well be 3ft, so pretty fine judgement based on your level of experience! Cheers, sim

PS

"use rudder close to ground" instead of yaw.

Rather strange advice since correcting for X-wind just before touch-down could be described using either term.

E.G. If cross wind is from left side, plane's nose will be counteracting it's effect by left heading to some degree. But the runway will be approaching from your right so you need to apply right RUDDER or YAW to the right to straighten the aircraft just before your wheels make contact. "Instead" is not the appropriate word as in this context "Rudder" or "Yaw" describe the same action.