Boeing 757 stabilities

[rhovsquared]

I was wondering about the aerodynamic stabilities possesed (flying qualities) in terms of positive negative or neutral. Spiral (before trimming as in early turns, and after trim), Lateral, Longitudinal, dutch roll qualities after YD failure? BTW can the mach trim/ stab runaway and if yes how do you stop it? I have a manual but no mention of this emergency (i dont have the QRH for type)

This is my second post (this is the aircraft I eventually want a TR in, when$$ permits I am a poor biochemist, but she is beautiful and looks very eager many thanks.

[ironbutt57]

Not smart enough to pass along highly technical info but to quote Boeing......"no mach tuck tendencies" during high speed dive cert tests..(conducted to .94 I believe), and there are in fact no operational limitations on yaw dampers, the QRH simply call for selecting the offending yaw damper to be switched off..be it one or both..

[rhovsquared]

Thanks your reply was very helpful wow M 0.94 with no tuck and no need for YDs (747 series too) wonder how boeing tamed the properties of sweep:cool: Btw, not really in need of precisely technical " Mr. Boeing-only-knows type of answers, a subjective impression will do;. I know the g limits with flaps are protected from thye stall to 40 deg. bank. I am still curious about the spiral qualities especially before directional and lateral trim at takeoff (i know this can vary, but overall)
no tuck at .94 M is a clue to very good longitudinal stability in the high altitude high speed regimes.

Just for discussion sake I am curious about everybodies plane Airbus, Boeing Douglass Lockheed I am a real nerd with these things. but I specifically asked about the 757 becuase I actually hope the fly it one day

Thanks again rhov

[Best foot forward]

Stab trim can run away and there are two cut out switches next to the power levers. Haven't heard of it failing. QRH doesn't mention any limits if one yaw damper fails, but MEL says the acft needs at least one of the yaw dampers. The acft is great to fly, good luck with the type rating, I know a couple of Biochemists that fly commercially. With the spiraling cost of drugs (medicinal type) I would have thought it would be well paid.

[Acomabird]

I was wondering about the aerodynamic stabilities possesed (flying qualities) in terms of positive negative or neutral.

Can't get to technical about this , but .. is one of the more "balanced" airplanes I have flown. (757-200). Alot has to do with how the plane is powered. The 757 has been my favorite to fly.It is a sweet flying airplane.

I am typed on the A310, F-100, MD80, 737-800, 757/767. The one funky thing about it is the yaw dampers. They have been toned down, but if you hit turbulence, and go reach for your coffee cup, you'll find your coffee everywhere besides in your cup. Some how the yaw dampers set up a "swirling" motion that will empty whatever you set in the the cup holder.

[Shore Guy]

I'm on the airplane, love it, but.....

Modifications to eliminate landing control anomalies

Boeing 757 operators will have to install control wheel damper as*semblies
and leading-edge vortex generators, or vortilons, to prevent roll
oscillations near touchdown, under a proposed US Fed*eral Aviation
Administration ruling.
The agency says 11 incidents have been reported where 757s experienced
unintended roll oscillations on final approach, just before landing. One
incident resulted in a nose gear collapse after a hard landing; another
involved a tail strike that ended in an aborted landing.

These roll oscillations occur when the pilot makes large, rapid movements of
the control wheel, and the aircraft does not respond as expected," says the
FAA in a notice of proposed rulemaking (NPRM). "Boeing has developed a
damper for the control wheel that reduces the likelihood of these roll
oscillations by providing resistive force to large, rapid control wheel
movements that exceed a set value."

Vortex generators can also reduce oscillations, the FAA says. "We have also
received flight-test data indicating that one potential cause of these
unintended roll oscillations occurs when airflow over the outboard
trailing-edge flap separates due to the movement of the spoilers resulting
from large control wheel inputs. Abrupt control wheel inputs to counteract
the resulting roll can lead to roll oscillations of increasing magnitude."

Boeing has developed vortex generators that "create vortices over the flap
surface and help to mitigate a sudden and premature airflow separation when
the flaps are set in landing configuration and the spoilers forward of the
flaps are deployed," says the NPRM.

The manufacturer has previously issued service bulletins recommending wheel
damper assembly and vortex generator installation.

The FAA notes that the proposed rulemaking is considered to be an interim
action, and that Boeing is "currently investigating an additional
modification that may further reduce or eliminate the unsafe condition...
Once this modification is developed, approved, and available, [the FAA] may
consider additional rulemaking."

Compliance is expected to cost between $4.8 million and $6.5 million for
installation of the wheel damper assembly on the 578 US-registered 757-200
derivatives, predicts the FAA. The cost for the 51 US-registered 757-300s in
operation is expected to be $588,000.

Vortex generator installations are expected to cost $2.1 million for
affected aircraft. The ruling will affect US-registered aircraft only. The
NPRM is open to public comment until 17 March.

From Flight Inernational......

[Jonty]

I read this too. A few years ago the company I work for installed vortex generators on flaps 30 to help with this problem and improve low speed stability, I have flown both with and without these generators and can honestly say they make no difference. It still wallows and feel like your flying a blamonge(sp?) at speeds below 125kts and it still feels very responsive at speeds above.

[rhovsquared]

thankyou all for very interesting and informative replies sound like a lady to marry. Btw just graduated so no $$$ just a lot of student loan debt for me::yuk: