acronym for Vmc factors

[Fly_Unity]

Ive seen studies that showed the difference in performance at different bank angles. The Seminole in an engine out has the best performance at 2.7 degrees of bank to be exact, I believe at 5 degrees of bank, there is a loss of 50 FPM from the 2.7 degrees of bank. Sure 5 degrees of bank has a lower VMC, but if you lose an engine, who cares about that as long as your above VMC speed, Many people I talk to always flys the full 5 degrees of bank in an engine out, which is only (maybe) slightly better performance as 0 degrees of bank in an engine out

[tgrayson]

Originally Posted by Fly_Unity

he Seminole in an engine out has the best performance at 2.7 degrees of bank to be exact, I

Melville Byington, a professor at Embry Riddle, did flight tests on a number of aircraft, including the Seminole. His figures:

                         Cessna           Piper         Beech
                       Crusader        Seminole      Baron 58
ZS Bank:                    1.5             2.1           2.7
Ball Defl:                   .3              .4            .7
ROC Change (0 to ZS)        +42             +62          +105
ROC Change (ZS to 5)        -91             -92           -76

His figures show that the ROC penalty for every degree over ZS is 26-33 fpm.

[PilotBeckfizzle]

S - Standard day @ sea level
M - Max power on operating engine
A - Aft CG
C - Critical engine prop windmilling
M - Most unfavorable weight (light)
U - Up to 5 degrees of bank into operating engine
F - Flaps/Gear Up

*Probably not a appropriate to say out loud if your DPE is a female.

[Fly_Unity]

Originally Posted by tgrayson

Melville Byington, a professor at Embry Riddle, did flight tests on a number of aircraft, including the Seminole. His figures:

                        Cessna           Piper         Beech Crusader        Seminole      Baron 58 ZS Bank:                    1.5             2.1           2.7 Ball Defl:                   .3              .4            .7 ROC Change (0 to ZS)        +42             +62          +105 ROC Change (ZS to 5)        -91             -92           -76

His figures show that the ROC penalty for every degree over ZS is 26-33 fpm.

Interesting

[VDEE7]

Originally Posted by tgrayson

The larger the HCL, the more of a sideslip to the good engine you have and the greater the directional control.

It's more of a paper reduction that a real one. In reality, you're going to be shooting for zero sideslip and won't be able to take advantage of the greater weight; it will only reduce your climb rate.

In all, better to be light, rather than heavy, no matter what it does to Vmc.

Are you saying that VMC wouldn't change between the light and heavy aircraft if both are banking for ZSS only?

[tgrayson]

Originally Posted by VDEE7

Are you saying that VMC wouldn't change between the light and heavy aircraft if both are banking for ZSS only?

Correct. The heavier aircraft will need less of a bank to achieve ZS. (The bank is correlated with the T/W ratio.)

[skycowboy]

How about:

Critical Engine Wind milling - increase in Vmc, drag, asym-thrust
Aft Center of Gravity - Increase in Vmc - less rudder moment
Standard day - aircraft is Vmc certified on standard day - nonstandard temps and pressures affect the Vmc
Take-off Configuration - Gear down acts as three vertical stabilizers thus lowering the Vmc
Bank 5 degrees into good engine (unless your in an MU-2), thus helping the zero-sideslip situation thus reducing drag, thus decreasing Vmc
Operating engine max power - asym thrust causes Vmc to increase
Weight most unfavorable - max gross + aft CG = bad = increase in Vmc

C
A
S
T
B
O
W

Four factors that determine critical engine:

P-factor
Accelerated slipstream
Spiraling slipstream
Torque

Hope this helps,

[VDEE7]

Critical Engine:
I'm not sure if this is correct but I heard that "Spiraling Slipstream" effect on directional control does not really exist! unless the airplane is in a slip!

[tgrayson]

Originally Posted by VDEE7

Critical Engine:
I'm not sure if this is correct but I heard that "Spiraling Slipstream" effect on directional control does not really exist! unless the airplane is in a slip!

If that's from our discussion of months ago, I had made the point that there was no evidence that slipstreams curve the way that some people show in their ME prep material; from everything I've ever seen slipstreams travel pretty straight. The only diagram that I've ever seen showing how a slipstream affects directional control showed the airplane in a slip.

That said, I would not discount the direction of prop rotation from producing slipstream effects on directional control. There are other ways this could happen beside having the slipstream curve. The slipstream itself widens at an angle of about 15 degrees; depending on the geometry, the edges of the slipsteam could have some influence on the vertical stabilizer. Even disregarding that, the propeller sidewash on the sides of the fuselage would mix with the relative wind, creating pressure differences on one side of the aircraft relative to the other, affecting directional control in some way. Unless I see some supporting data, I'm skeptical whether these phenomena produce consistent effects across all airplanes.

I probably woudn't recommend someone walking into a checkride with this degree of agnosticism, but I'd also rather not see them drawing a curving slipstream!

[Fly_Unity]

Originally Posted by tgrayson

I probably woudn't recommend someone walking into a checkride with this degree of agnosticism, but I'd also rather not see them drawing a curving slipstream!

The Turbine Pilot's Manual shows a diagram of a curving slipstream, I doubt that anyone would bust a checkride because of that, though I agree that there is no evidence for it, I never even thought about it accuring in a slip though.

[tgrayson]

Originally Posted by Fly_Unity

The Turbine Pilot's Manual shows a diagram of a curving slipstream, I doubt that anyone would bust a checkride because of that, though I agree that there is no evidence for it, I never even thought about it accuring in a slip though.

The author of that book isn't a technical guy and I suspect he's just passing on stuff that "he heard somewhere." Books written by those who are pilots-only are generally unreliable on technical matters, unless he has well-documented sources of authoritative information. Greg Brown has never impressed me in that way, which is why I've never bought the Turbine Pilot's Manual. Does he show any footnotes regarding his sources?

[ppragman]

that's good, I used "smacmuf" because I'm immature

[wan2fly]

LCWBFATCOPS (ELSIE WILL BUY FAT COPS)

L Landing gear retracted
C Center of gravity most unfavorable (aft & away)
W Weight, most unfavorable (light)
B Bank, not to exceed 5 degrees
F Flaps (Take off position specific to aircraft (usually UP)
A Altitude Most critical mode of failure (standard sea level density altitude) (23.45, max
10,000' this is for performance data)
T Take-off Power (on each engine)
C Configuration, (Take-off) again 23.45 dealing with the cowl flaps and performance data)
O Out of Ground Effect (More induced drag requiring higher AOA. Increased AOA =
increased P-factor = higher Vmc. Closer to critical AOA.
P Propeller, Windmilling
S Standardization, Vmc not to exceed 1.2 Vs1 / Max of 20 degrees of heading loss / Max
of 150 lbs rudder pressure

Don't forget aircraft under 6000lbs or Vso of 61 kts or less there is no requirement for a positive rate of climb performance data. Just needs to be determined.

[trafficinsight]

Originally Posted by BuickCFI

i was looking at the data sheet for the PA-30 and PA-39 twin commanche's and the PA-30 has a higher Vmc speed (it was under CAR 3 regulations) BUT it also has a critical engine, whereas the PA-39 looks like it has counter-rotating props. The PA-39 was certified under Part 23(i think, but i might have misread)

edit: nevermind, looks like they were all certified under CAR 3, how does that work when the FAR's were in effect in 1965 IIRC?

Any changes to a type can be added to the original type certificate without recertification.

For example, Type Certificate number 3A12 was originally approved on December 14th 1956 and last amended February 5th 2008. It covers the entire 172 series.

So, even though the new 172s meet Part 23 standards, they are certified under CAR 3