Flying backwards causes gyrations?

[John Doe]

I recall hearing mention of something like this before. While doing a
simulation, probably moving backwards, the helicopter tale began
swaying back and forth uncontrollably.

Is that the way it is in real life?

How do you get out of that? Avoid moving backwards?

Besides trying to tilt the chopper forwards, is there anything to do
when the gyrations first began? When gyrations become extreme, is there
any way out? I suppose structural damage is possible?

Thank you.

[John_F]

When flying backwards you have horizonal and vertical tail surfaces
flying backwards. As long as they are aligned perfectly into the
relative wind every thing is ok, however this is not a stable
condition. They want to fly BEHIND the aircraft. When a slight
offset occurs it will get larger fast as the tail tries to turn around
so that it is again behind the helicopter which is stable. If you do
the pedal dance correctly you can keep the error small and you will
have enough tail rotor power to keep the tail pointing into the wind.
If you screw up and let the error get too large the tail will come all
the way around because there is not enough tail rotor power to stop
the turn. The worse problem occurs when the tail tries to go up or
down to realign. This will force the tail into the dirt or the sky,
both are bad. If the tail goes up it may lead to a tail boom strike
by the main rotor. If down the tail rotor eats dirt.
John

On Sat, 15 Jan 2005 04:33:16 GMT, John Doe
> wrote:

>I recall hearing mention of something like this before. While doing a
>simulation, probably moving backwards, the helicopter tale began
>swaying back and forth uncontrollably.
>
>Is that the way it is in real life?
>
>How do you get out of that? Avoid moving backwards?
>
>Besides trying to tilt the chopper forwards, is there anything to do
>when the gyrations first began? When gyrations become extreme, is there
>any way out? I suppose structural damage is possible?
>
>Thank you.

[John Doe]

Thanks. For what it's worth, I am using Microsoft's Flight Simulator
2004 stock helicopters.

(John_F) wrote:

>When flying backwards you have horizonal and vertical tail
>surfaces flying backwards. As long as they are aligned perfectly
>into the relative wind every thing is ok, however this is not a
>stable condition. They want to fly BEHIND the aircraft. When a
>slight offset occurs it will get larger fast as the tail tries to
>turn around so that it is again behind the helicopter which is
>stable. If you do the pedal dance correctly you can keep the error
>small and you will have enough tail rotor power to keep the tail
>pointing into the wind. If you screw up and let the error get too
>large the tail will come all the way around because there is not
>enough tail rotor power to stop the turn. The worse problem
>occurs when the tail tries to go up or down to realign. This will
>force the tail into the dirt or the sky, both are bad. If the
>tail goes up it may lead to a tail boom strike by the main rotor.
>If down the tail rotor eats dirt.
>John

[Andrew Crane]

"John Doe" > wrote in message
...
> Thanks. For what it's worth, I am using Microsoft's Flight Simulator
> 2004 stock helicopters.

It's broken. Real helicopters don't oscilate from a point ten yards behind
the tail as soon as you slow up (you don't even have to be going backwards
for it to start doing that). MSFS doesn't model helicopters. Try X-Plane
which is a thousand times closer to the real thing (but still some way to
go).

Regards
Andrew

[JIM105]

Not a computer guy, but I would think Microsoft is basing the helicopter
program on their fixed-wing with minor differences. Of course the programmers
never have to worry about airplanes flying backwards so they don't model the
program for that.

For what it's worth, in real life there is very little need to fly a helicopter
backwards at any speed. Would you drive your car in reverse at 40 mph? I
would'nt do that with my helicopter either. Military ops excluded of course.
Just for the heck of it, I have taken an S-76 sim at FlightSafety backwards at
high speed. Made me nauseous!

[Paul Probert]

I had a big problem with flying backwards in Microsoft Flight Simulator, but
when I got a new computer with a fast video board the problem went away. It
was a pilot induced oscillation caused by the time lag between control input
and visual feedback.

Paul Probert

John Doe wrote:

> Thanks. For what it's worth, I am using Microsoft's Flight Simulator
> 2004 stock helicopters.
>
> (John_F) wrote:
>
>
>>When flying backwards you have horizonal and vertical tail
>>surfaces flying backwards. As long as they are aligned perfectly
>>into the relative wind every thing is ok, however this is not a
>>stable condition. They want to fly BEHIND the aircraft. When a
>>slight offset occurs it will get larger fast as the tail tries to
>>turn around so that it is again behind the helicopter which is
>>stable. If you do the pedal dance correctly you can keep the error
>>small and you will have enough tail rotor power to keep the tail
>>pointing into the wind. If you screw up and let the error get too
>>large the tail will come all the way around because there is not
>>enough tail rotor power to stop the turn. The worse problem
>>occurs when the tail tries to go up or down to realign. This will
>>force the tail into the dirt or the sky, both are bad. If the
>>tail goes up it may lead to a tail boom strike by the main rotor.
>>If down the tail rotor eats dirt.
>>John
>

[Simon Robbins]

"John Doe" > wrote in message
...
> Thanks. For what it's worth, I am using Microsoft's Flight Simulator
> 2004 stock helicopters.

Download the AS350 from AvSim.com. It's a lot more convincing than either of
the stock helicopters, and can be flown backwards a little easier. Certainly
more forgiving than the B206 and it has nice turbine start-up and shutdown
operation. There's a good AS365 on there too but I find it a bit too
flighty.

I had a weird experience "flying" the AS350 the other day. I figured since
it's got a nice composite rotor head I'd try and loop it. First attemp I
dived down, maintaining a +ve G and pulled back, rolling off the collective
as it went inverted and I made it. Second attempt I lost airspeed and it
fell... upwards!! In about a 5 minutes I was at 100k feet and zero G.
Isn't it about time the real world built helicopters like Microsoft can
model them? Imagine the fun to be had!

(Oh, and if you tire of drilling holes in the floor with your tail rotor,
for kicks take a look at the "Firefox" model at either AvSim or
www.thinkinrussian.org. )

Si