Slips

[PT20J]

The point about Fowler flaps is that they must significantly increase the area of the wing in addition to deflecting downward to be classed as Fowler.

There was an old trick used by 727 pilots when they were heavy and wanted to climb higher. They would pull the slats CB and select Flaps 2. This caused the flaps to travel back fully thereby increasing the wing area without the slats extending as would normally happen. The larger wing could now climb higher on the thrust available. One of my airline pilot buddies told me that every 727 he flew had a worn spot around the slat breaker.

[Andy95W]

2 hours ago, A64Pilot said:

 

  What I call a poor man’s Fowler can be made by significantly dropping the hinge point, look at a Husky for an example, the dropped hinge point moves the flap aft opening up the slot.

 

You don’t have to look at a Husky, just look at your Mooney wing and its flap attachments.

[0TreeLemur]

8 hours ago, PT20J said:

The point about Fowler flaps is that they must significantly increase the area of the wing in addition to deflecting downward to be classed as Fowler.

There was an old trick used by 727 pilots when they were heavy and wanted to climb higher. They would pull the slats CB and select Flaps 2. This caused the flaps to travel back fully thereby increasing the wing area without the slats extending as would normally happen. The larger wing could now climb higher on the thrust available. One of my airline pilot buddies told me that every 727 he flew had a worn spot around the slat breaker.

And then there was TWA 841.   While the FE was taking a leak, the Cap'n pulled the Slats CB to do just this.  The FE re-entered the cockpit, saw the Slats CB was popped and pushed it back in just before the Cap'n selected Flaps 2.

That 727 went into a vicious spiral dive as one of Slats departed the aircraft, losing 34,000 ft in 63 seconds.  Luckily everyone walked away.

https://simpleflying.com/twa-flight-841-sudden-dive-1979/

A great study in CRM CYA.

[Pinecone]

16 hours ago, PT20J said:

Two perpetual myths about Cessnas are that slips with flaps are dangerous and that they have Fowler flaps.

According to Cessna, the flaps are "single slotted". This is a common oral question on the practical test. If you say Fowler, you get to look it up in the POH.

A Fowler flap is one that the flap moves aft as it goes down.  Cessna flaps do this.  They are technically a single slotted Fowler flap.

 

 

[Pinecone]

10 hours ago, PT20J said:

Actually, most trim drag is from the wing -- it is the increment of induced drag created by the extra lift required to offset the tail down force.

You have that backwards.  Trim drag is from induced drag created by the tail in countering the main wing forces caused by the center of pressure being aft of the CG.   The more main wing pitching forces, the more counter lift (downwards) by the tail which increases induced drag.

This is why aft CG is faster.  The CG is closer to the wing center of pressure, so less pitching force, needing less tail force to counter act.

The fastest CG position would be where the CG was at the same chord point as the center of pressure.  But the plane would be unflyable.

[PT20J]

16 minutes ago, Pinecone said:

You have that backwards.  Trim drag is from induced drag created by the tail in countering the main wing forces caused by the center of pressure being aft of the CG.   The more main wing pitching forces, the more counter lift (downwards) by the tail which increases induced drag.

This is why aft CG is faster.  The CG is closer to the wing center of pressure, so less pitching force, needing less tail force to counter act.

The fastest CG position would be where the CG was at the same chord point as the center of pressure.  But the plane would be unflyable.

Well actually, trim drag comes from both the tail and the wing. Any lifting surface of finite span produces induced drag. The tail, “lifting” downwards, will necessarily produce some drag. The wing must have increased lift to balance out the tail down force and this will incrementally increase the induced drag of the wing.

But, my point was that trim drag is not parasitic drag caused by the elevator not being aligned with the stabilizer.

Skip

[Pinecone]

Agreed.

[A64Pilot]

23 hours ago, Pinecone said:

 

The fastest CG position would be where the CG was at the same chord point as the center of pressure.  But the plane would be unflyable.

It won’t come close to meeting FAA stability in pitch, but it’s usually flyable, you would be at what’s called the stick force neutral point, which means it essentially takes zero force to move the yoke in pitch, you just have to be careful and not let go of the controls for any reason, if you go further aft of the stick force neutral point the flight control can go full travel one way or the other all on its own, it will actually pull to go full travel, the further it’s displaced the harder it will pull.

Very often in small airplanes the stick force or rather lack of it is what determines aft CG limit, thats when you add springs, anti servo tabs, bob weights etc to artificially increase stick force gradient. The FAA requires that the more the control is displaced there has to be an increasing force to do it, no 1970’s US car power steering allowed. The further aft the CG also the more maneuverable the aircraft, because it’s less stable, most every crop duster we built left the factory ballasted to the aft CG limit with full fuel, 170 lb pilot and empty hopper (worst CG load)

An airplane is required to be positively stable in yaw and pitch and neutral in roll, meaning of course it will recover on its own in pitch and yaw and remain banked if controls are released.

What I find interesting in this is, a helicopter is negatively stable in ALL axis, yet we fly them everyday, safely. Though most have a “force trim” system that adds springs to assist in the flight control being returned to center, on some that system can be turned off and many pilots fly with it off.

[PT20J]

3 hours ago, A64Pilot said:

What I find interesting in this is, a helicopter is negatively stable in ALL axis, yet we fly them everyday, safely.

Even more interesting is that I could learn to hover the darn thing. What you want is to control position, but the cyclic tilts the lift vector which is a force and thus you are controlling acceleration. 

[A64Pilot]

1 hour ago, PT20J said:

Even more interesting is that I could learn to hover the darn thing. What you want is to control position, but the cyclic tilts the lift vector which is a force and thus you are controlling acceleration. 

You overthink things, it doesn’t matter how, just do whatever is necessary to hold position, for the un-initiated it goes something like this.

You want to hover so you lift up the collective, this causes the rotor to droop so you have to add throttle, to keep from spinning in a circle it takes left pedal input, this keeps the thing from spinning, but it also shoves it to the right, so you have to input left cyclic which reduces lift vector, so more collective which means more throttle which means more left pedal, which shoves the thing sideways again. over and over

OK so you get that down and you want to fly so you push cyclic forward, your reducing lift vector again so the aircraft begins to settle so we do that whole collective, shoved to the right drooping rotor thing and throttle thing again, as you begin to move quickly first there is a shudder caused by transverse flow effect, then it lifts like you hit a thermal caused by translational lift, but also at the same time the aircraft begins to slow caused by rotor blow back, so you really have to add more cyclic to keep accelerating or it slows and goes back into a hover

But due to transverse flow effect, translating tendency, blow back etc to maintain runway alignment your actually moving the cyclic initially forward, then in a sort of circle to the right as well as forward.

First time I flew a French helicopter I thought it was going to give me a lot of trouble, because their rotor spins opposite US designs which means of course opposite pedal is required and after awhile it seems in a US design your left hand is connected to your left foot, that is when you add collective you just automatically add the correct pedal input, but if you don’t think about it, your feet will just do whatever is necessary to keep the nose pointed straight.

It’s when you try to reason it out that you get into trouble, you can’t possibly think fast enough it has to just happen, like riding a bicycle.

We never leaned a helicopter engine, touching the red knob was prohibited, we always flew full rich, but a IO-360 in a helicopter is working hard all of the time, from memory we ran them at 2900 RPM I think.

[Pinecone]

Or, in the modern world you can make a plane negatively stable but add a computer to add enough artificial stability to fly it easily, but keep the high maneuverability intact.

The first one like this was the F-16

[PT20J]

35 minutes ago, A64Pilot said:

You overthink things, it doesn’t matter how, just do whatever is necessary to hold position, for the un-initiated it goes something like this.

You want to hover so you lift up the collective, this causes the rotor to droop so you have to add throttle, to keep from spinning in a circle it takes left pedal input, this keeps the thing from spinning, but it also shoves it to the right, so you have to input left cyclic which reduces lift vector, so more collective which means more throttle which means more left pedal, which shoves the thing sideways again. over and over

OK so you get that down and you want to fly so you push cyclic forward, your reducing lift vector again so the aircraft begins to settle so we do that whole collective, shoved to the right drooping rotor thing and throttle thing again, as you begin to move quickly first there is a shudder caused by transverse flow effect, then it lifts like you hit a thermal caused by translational lift, but also at the same time the aircraft begins to slow caused by rotor blow back, so you really have to add more cyclic to keep accelerating or it slows and goes back into a hover

But due to transverse flow effect, translating tendency, blow back etc to maintain runway alignment your actually moving the cyclic initially forward, then in a sort of circle to the right as well as forward.

First time I flew a French helicopter I thought it was going to give me a lot of trouble, because their rotor spins opposite US designs which means of course opposite pedal is required and after awhile it seems in a US design your left hand is connected to your left foot, that is when you add collective you just automatically add the correct pedal input, but if you don’t think about it, your feet will just do whatever is necessary to keep the nose pointed straight.

It’s when you try to reason it out that you get into trouble, you can’t possibly think fast enough it has to just happen, like riding a bicycle.

We never leaned a helicopter engine, touching the red knob was prohibited, we always flew full rich, but a IO-360 in a helicopter is working hard all of the time, from memory we ran them at 2900 RPM I think.

And I overthink things? 

[A64Pilot]

1 hour ago, PT20J said:

And I overthink things? 

We were taught all of that in ground school, before we ever even saw the TH-55, so first day I knew I’d never make it, no way could I remember all of that and do it in time.

Having been taught all that of course your running all of it through your head, and you fail.

What helped me was to be given only one flight control, say just the cyclic, I could handle that of course then play with the collective for awhile, then the throttle and finally the nose pointers. All four together took awhile.

It all came together of course, it just sort of becomes muscle memory, you think about where you want to go and how to get there, but don’t think about control movements

[PT20J]

1 minute ago, A64Pilot said:

We were taught all of that in ground school, before we ever even saw the TH-55, so first day I knew I’d never make it, no way could I remember all of that and do it in time.

Having been taught all that of course your running all of it through your head, and you fail.

What helped me was to be given only one flight control, say just the cyclic, I could handle that of course then play with the collective for awhile, then the throttle and finally the nose pointers. All four together took awhile.

It all came together of course, it just sort of becomes muscle memory, you think about where you want to go and how to get there, but don’t think about control movements

That’s how I learned, too. My point wasn’t really about thinking about it but about the fact that inherent instability combined with the way you control it is what makes it hard to learn. I flew an R44 with HeliSAS and a governor and probably anyone could learn to hover it in a couple of hours.