In addition--- since the A330 shifts modes during the landing, slipping the aircraft becomes a bit of a challenge, and could be the attributing factor to the A330 Crosswind Landing Statistics mentioned yesterday.
The handling differences in a Fly-By-Wire aircraft are significantly different in some maneuvers--- especially Landing.
If a slip is to be flown just before landing, lateral stick input is used to establish the amount of bank and must be returned to a neutral position to hold the amount of bank requested, while opposite rudder is established. Not a big deal. Now we're flying neutral stick with a bank established and cross rudder, creating a slip.
Normal Law--- the flight control law used for normal operations when everything is working.
Normal Law has three modes of operation:
- Flight Mode
- Landing Mode
- Ground Mode
Landing Mode is when the logic begins to change. Airbus decided that when descending below 100 feet RA, they wanted to give us a "conventional feel" for the flare and touchdown. This feel only effects the pitch handling characteristics. Then at 50 feet RA a slight pitch down elevator input is applied requiring the pilot to give a bit of aft stick movement to maintain the same pitch.
At 30 feet--- flare. The pilot brings the nose up just enough to arrest the descent rate. Not the traditional flare that you'd expect in a Cessna or a B747. Bring the power to idle when commanded. The aft mains touchdown first. Front mains land second. Then we fly the nose to the runway. Do not hold the nose off. If we hold it off too long, we'll run out of airspeed and she'll drop hard.
During the flare, rudder should be applied to align the aircraft with the runway heading.
Ground Mode is where the fun begins in crosswind conditions. Sidestick control of elevators, ailerons, and spoilers, is now directly proportional to the deflection of the sidestick. Therefore, if we had a bank established, but our stick was neutral--- once on the ground we'd be required to input the same amount of bank as necessary to counteract the wind, and hold the stick in that direction.
If you had no bank established, once on the ground, you may need to add some, remembering the direct stick to controls logic--- just like Direct Law. The flying does not stop when this plane is on the ground. It may just begin.
Tonight--- Pilots For Kids! Delta Pilots visit Childrens Hospital in Seatlte. More about that tomorrow!
~Enjoy the Journey!
Karlene~
"Flies just like a Cessna!" favorite comment of one of my friends who flies an Alaska 737 always says.
ReplyDeleteTom
Hi Karlene, whats the process for increasing or decreasing bank once the stick is neutral whilst still on the approach?.
ReplyDeleteYes! The only Boeing I've flown that doesn't land like a Cessna was the 727. You actually had to roll her forward on the mains to get a good landing. Timing was everything. But it's been a long time since I flew her.
ReplyDeleteThis is why I wrote the "Fly by Wire Perspective" found in your A330 Vol II page 17.10.2. In part (a small part):
ReplyDeleteThere are certain differences, however, that must be kept in mind when hand flying the
aircraft:
In general, only light fingertip pressure is required to smoothly execute most hand flying.
Remember, you are commanding a result (g load or roll rate) and not a flight control
deflection. Due to the mass of the aircraft and other factors, there is some small delay
between the stick input and when the resultant performance is achieved. Rapidly
moving the stick, especially in large alternating direction motions is most likely to result
only in pilot induced turbulence and difficulty flying the airplane precisely.
In the landing phase many pilots tend to use larger control inputs than in higher speed
phases of flight. Again, the roll and pitch rates are the same regardless of speed, so
large inputs are usually counterproductive. In gusty or turbulent conditions, the aircraft
is already trying to maintain a zero roll rate and is automatically making flight control
deflections to do so, and it is doing so with no feedback to the sidestick. Pilot inputs
other than those needed to correct the trajectory of the aircraft are usually unnecessary
and likely to result only in pilot induced turbulence and difficulty flying the airplane
precisely.
and....
The flying of some maneuvers is significantly different and the flight control laws must
be kept in mind when flying them.
For example, during crosswind landings if a slip is to be used just prior to landing, it is
important to realize the control input differences from a conventional aircraft. While in a
conventional control aircraft aileron needs to be held in as the rudder is applied, with
the Airbus fly-by-wire flight controls, lateral stick input only needs to be made to
establish the desired bank angle and then the stick must be returned to neutral to
command zero roll rate. After the bank is established and the stick returned to neutral,
the aircraft will automatically hold the aileron in when the opposite rudder is applied in
order to maintain the bank angle. Failure to return the stick to neutral will command an
continued roll rate and quickly result in excessive bank for the maneuver. Upon landing,
when the flight controls revert to ground mode (direct law), the stick will have to be
moved into the wind just to keep the aileron deflection the same, because in the ground
mode the relationship between the stick and the flight control surfaces is the same as
a conventional aircraft, neutral stick commands neutral aileron. Leaving the stick in
neutral after the initial touchdown may result in the upwind wing rising, as it is equivalent
to returning the control inputs to neutral upon touchdown in a conventional control
airplane.
Thank you Flybywire! This is great information and excellent reminders before I fly again. And... deserves a major shout for the other #A330 pilots out there.
ReplyDeleteHi Karlene,
ReplyDeleteThis is a great article. The only time I flew as a passenger in an A-330 was transatlantic to and from Europe. Do you prefer flying Boeing or Airbus aircraft in general? P.S. how do you get all of these fantastic experiences in different aircraft?
Good Morning Rory! I have to say from a "flying" perspective, I love flying the Boeing 747-400. She fly's like a great big Cessna. And, you feel like you're flying. The Airbus... fly by wire... is different technology. Brilliant and does some great things. And... I'm loving flying her too. Actually, learning her nuances is fun. I think when I completely figure her out, she could be my favorite. Until the next Boeing I fly. Love the plane you're with.
ReplyDeleteThe trick to getting great experiences in wonderful airplanes is to work at many airlines. While some may not think that's a good idea for career advancement, sometimes life throws at you what it will ...furloughs, bankruptcy, layoffs...and if you embrace it, all is good.
Happy Holidays and Thank you for the comment!