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Businessjet93
01-01-2019, 07:27 PM
According to "Plane flying handbook" Slipstream does not effect to nose wheel plane much but does effect tail wheel plane pretty much.

Why?


JohnBurke
01-01-2019, 10:04 PM
Do you mean "spiraling slipstream," as in the effect of the airflow from the propeller?

In flight, there's really no difference between a conventional gear airplane (tailwheel) and one with a nosegear.

On the ground, whether the tailwheel is touching the ground or in the air, airflow from the propeller affects the airplane, but it affects airplanes with a nosewheel, too.

When a takeoff is started, with a typical clockwise propeller rotation (as seen from the cockpit), right rudder is required. This is true of conventional gear and nosewheel equipped aircraft. Rudder effectiveness is low at slow speeds, but is improved by application of prop wash, or propeller slipstream.

There are three forces to which textbooks often reference rudder use on takeoff or in flight; spiraling slipstream, torque, and asymmetric thrust, which is somewhat of a misleading term in a single engine airplane, but also not incorrect.

With all three wheels on the ground in a conventional gear airplane, it behaves much like a nosewheel airplane does when the nosewheel is on the ground. With the tailwheel in the air and the mains on the ground, the airplane behaves much like a nosewheel airplane when the nosewheel is in the air. Not a lot of difference.

A nosewheel tends to be a bit more forgiving under certain conditions, but a tailwheel equipped airplane isn't really any more difficult to fly. The forces of flight affect each airplane the same. There is a brief period of time when the rudder loses effectiveness as one slows that the airplane may be a bit more vulnerable to mishandling or gusts, but the rudder can be quickly energized with propeller-induced airflow, and if the airplane has differential brakes, they aid in directional control until the tailwheel reaches the ground.

The big difference is that in a nosewheel airplane, generally the nose will stay on the ground until positively raised, whereas the tailwheel airplane will typically fly the tail with adequate airflow (propeller slipstream, gusts, etc) unless it's held down.

TiredSoul
01-02-2019, 10:16 AM
When a nose wheel airplane rotates the gyroscopic effect counteracts left turning tendencies and in a tailwheel aircraft when the tail comes up gyrospic effects enhance left turning tendencies.


JamesNoBrakes
01-02-2019, 03:43 PM
Corkscrew Effect
The high-speed rotation of an aircraft propeller gives a
corkscrew or spiraling rotation to the slipstream. At high
propeller speeds and low forward speed (as in the takeoffs
and approaches to power-on stalls), this spiraling rotation
is very compact and exerts a strong sideward force on the
aircraft’s vertical tail surface. [Figure 5-48]
When this spiraling slipstream strikes the vertical fin, it
causes a yawing moment about the aircraft’s vertical axis.
The more compact the spiral, the more prominent this force
is. As the forward speed increases, however, the spiral
elongates and becomes less effective. The corkscrew flow
of the slipstream also causes a rolling moment around the
longitudinal axis.
Note that this rolling moment caused by the corkscrew flow
of the slipstream is to the right, while the yawing moment
caused by torque reaction is to the left—in effect one may
be counteracting the other. However, these forces vary
greatly and it is the pilot’s responsibility to apply proper
corrective action by use of the flight controls at all times.
These forces must be counteracted regardless of which is
the most prominent at the time.

This is from the PHoAK.

A conventional gear airplane is inherently unstable during part of the takeoff run due to the gear configuration, push a tricycle backwards and try to keep it straight, same principle. Airplanes are stable about the vertical axis in flight and will weathervane into the relative wind if displaced, except a conventional gear airplane will further displace when an outside force acts on it until it gets fast enough for this effect to take place. There is a critical speed range with a conventional gear airplane that you have to accelerate through to get to that weathervane-range, if something happens at the lower speed, you may not be able to control the aircraft or keep it from going further in the direction it was displaced.

The exact effect of the "corkscrew" depends specifically on that airplane's configuration and the effect, it's not a very "consistent" force in that idea, between different types of airplanes and configurations. Such as, the aircraft may be trying to roll right, but that puts more weight on the right tire, which creates more drag to the right, counteracting the yawing moment. Or you may have the tail more blanked out, or more exposed, etc...

I guess it's worth a mention in the PHoAK, but with it being so variable in the effects, it's not worth a lot of time spent on it. You won't be able to discern it from the more primary effect, p-factor. Kind of like torque, it's not like when you push the throttle up the plane rolls inverted to the left and in steady RPM state there is no "acceleration" in the opposite direction. The plane is way way heavier and is going to "win" during RPM change, except in some extreme situations you will definitely get this effect, such as a very high HP single with a massive prop, like a WWII fighter. The most this is usually going to affect anyone is a little more weight on one of the tires during the initial RPM spool-up. Spiraling slipstream/corkscrew really gets "into the weeds" IMO and unless you are an aeronautical engineer, you can't go very far with it.

JohnBurke
01-03-2019, 12:01 AM
I fly single engine airplanes with clockwise and counterclockwise propellers, with large radials and large props, and smaller, nosewheel and conventional gear.

One can really overthink it, and there's so much out there about tailwheels "making a real pilot" and being "difficult" to fly that the truth gets lost in the hype. The reality is that it doesn't make much, if any difference.

I flew a large single engine airplane to an airport where a pilot proceeded to tell me all about how large tailwheel airplanes with big propellers would torque roll right out from under a pilot and all kinds of other things she'd heard. Then she asked if it was all true.

Not that I'd noticed. Tail up, tail down, nose up, nose down...Some airplanes want to turn left, some right. Use opposite rudder, whatever is needed, and when you run out of rudder, you've got brake or angling across the runway or using a taxiway or a different runway...and that's about it. They don't operate that differently. Same for flying floats, which are different than nosewheels or tailwheels, but don't fly much differently, including the amphibians, which have four wheels, two on each float (or tricycle gear or conventional gear for some amphibs). Not really that much different to operate.

rickair7777
01-03-2019, 05:43 AM
I fly single engine airplanes with clockwise and counterclockwise propellers, with large radials and large props, and smaller, nosewheel and conventional gear.

One can really overthink it, and there's so much out there about tailwheels "making a real pilot" and being "difficult" to fly that the truth gets lost in the hype. The reality is that it doesn't make much, if any difference.

I flew a large single engine airplane to an airport where a pilot proceeded to tell me all about how large tailwheel airplanes with big propellers would torque roll right out from under a pilot and all kinds of other things she'd heard. Then she asked if it was all true.

Not that I'd noticed. Tail up, tail down, nose up, nose down...Some airplanes want to turn left, some right. Use opposite rudder, whatever is needed, and when you run out of rudder, you've got brake or angling across the runway or using a taxiway or a different runway...and that's about it. They don't operate that differently. Same for flying floats, which are different than nosewheels or tailwheels, but don't fly much differently, including the amphibians, which have four wheels, two on each float (or tricycle gear or conventional gear for some amphibs). Not really that much different to operate.


Yeah mostly you instinctively add in whatever minor corrections are needed for any aerodynamic effects. A student pilot in a P-51D might need to be thinking ahead, but outside of extreme cases it's mostly just second nature.

JamesNoBrakes
01-03-2019, 09:11 AM
Not really that much different to operate.

It's true, but there's always a subset out there that "doesn't get it". As they fly higher and higher performance aircraft, the results of their performance diverge more and more from what is "acceptable". I've always heard how landing such and such airplane is this and that and almost every time, it lands just like you'd expect an aircraft to land if you are using the right visual and sensory cues. There are a few quirks out there, but never to the extent that supports the hype IME.

For those that "don't get it", it is different to operate, but those are the type of people that should be happy in their current simple airplane and should exercise extreme caution and get help when they want to fly something else.

sailingfun
01-08-2019, 05:05 AM
[QUOTE=JohnBurke;2735659]I fly single engine airplanes with clockwise and counterclockwise propellers, with large radials and large props, and smaller, nosewheel and conventional gear.

One can really overthink it, and there's so much out there about tailwheels "making a real pilot" and being "difficult" to fly that the truth gets lost in the hype. The reality is that it doesn't make much, if any difference.

Accident statistics and insurance costs would argue against the above statement. A nose wheel aircraft will kick itself straight on touchdown if the fuselage is not properly aligned with the runway because the main gear are further aft. A tail wheel aircraft does the opposite and requires you actually use your feet. In addition a tailwheel aircraft has a limited amount of weight on the tailwheel relative to the amount of weight on a nosewheel aircraft. This gives the nosewheel aircraft better stability on the ground.
The last issue varies between aircraft types but tailwheel aircraft often have very limited visibility in the landing attitude. Some like the Pitts almost mandate a curved base to final and perhaps a slip for visibility.

JohnBurke
01-08-2019, 11:13 PM
A nose wheel aircraft will kick itself straight on touchdown if the fuselage is not properly aligned with the runway because the main gear are further aft.

It doesn't make any difference if you touch down on the mains. In fact, the third wheel doesn't come into play until it touches down. By then, one should have got it figured out.

A normal flare in a nosewheel aircraft is a normal three point landing in a tailwheel aircraft. Again, not a lot of difference.

Nosewheel aircraft (some) allow a bit more slop in one's behavior. Then again, there are nosewheel aircraft which require one to be on top of it all the way, and that won't track straight ahead more than a few feet before taking off in a turn. I've flown them.

A tail wheel aircraft does the opposite and requires you actually use your feet.

Pretty much any aircraft, actually. We get lazy in turbojet equipment and some actually put their feet on the floor.

The rudder is there to be used as needed. Again, it's not inherently different in a conventional gear aircraft vs. a nosewheel aircraft.

In addition a tailwheel aircraft has a limited amount of weight on the tailwheel relative to the amount of weight on a nosewheel aircraft. This gives the nosewheel aircraft better stability on the ground.


It really doesn't. There's some difference in aircraft with locking tailwheels (try landing an 802 with the tailwheel unlocked in a crosswind. That will make your day). Otherwise, landing, taxiing, and flying a conventional gear airplane really isn't that much harder or difficult; once the tail is in the air, it's essentially the same, and so far as taxiing...well that's just taxiing. Not really particularly complicated either, nor unstable.


The last issue varies between aircraft types but tailwheel aircraft often have very limited visibility in the landing attitude.

Not really. Much ado about nothing, especially if one does a two-point landing. Problem solved.

sailingfun
01-10-2019, 09:04 AM
I gather when you got your tailwheel endorsement you did not get much of a groundschool. Tailwheel aircraft behave very different from nosewheel aircraft on the ground. The main reason is the placement of the main gear relative to the Center of mass. It’s basic physics. A secondary issue is weight on the third wheel. A tertiary issue is a tailwheel aircraft generates lift in its normal ground attitude putting less overall weight on all the gear.
Visibility is good in most tailwheel aircraft if doing a wheel landing however in some tailwheel aircraft wheel landings are not recommended or even prohibited due to prop diameter and or type of main gear construction. A Pitts is a good example. 3 point landings are also mandated on short fields and a pilot is required to be proficient in both types to get a tailwheel endorsement.
The last point is the most salient. There are several types of aircraft that can be conventional or nosewheel depending on how it’s ordered or built. You will always pay more in insurance for the conventional gear aircraft because despite being generally flown by more experienced pilots the accident rate for landings and takeoffs is substantially higher with the tailwheel.

Here is a simplified primer on tailwheel aircraft.
On the ground, tailwheel aircraft are naturally unstable because the center of gravity is located aft of the main landing gear. Ever tried to push a tricycle backward? With the slightest turn, the tricycle wants to veer to one side or the other, or spin. That’s how a tailwheel behaves moving forward.

“The important thing with the tailwheel is that you have to keep the nose straight, so the airplane has to be pointed in the same direction that it’s going,” Rapp explained. That’s easier said than done. “Anytime a divergence starts to develop between those two things, you’re going to see that ground looping tendency.” The key to correct drifting off center on the runway or taxiway without ground looping is to stop the drift before bringing the aircraft back to the desired position. Holding the rudder too long or swerving could set you up for a ground loop.

JohnBurke
01-10-2019, 11:13 AM
I gather when you got your tailwheel endorsement you did not get much of a groundschool.

Thank god you're here to educate me.

I don't have a tailwheel endorsement.

Think about it.

Thanks for the primer, though, and I'm glad you simplified it. After several decades of flying conventional gear aircraft, teaching in them, fighting fire in them, spraying crops in them, doing aerobatics in them, towing in them, etc, the primer helped out a lot.

Ground looping "tendency," huh?



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