Capt Kay
5. Boeing
777 Questions on TAC, Protection, Auto Throttle and E-Checklist.
Monday, June 10, 2002 2:26 PM
Hi Capt Kay,
How are you? Remember me? I am the guy who asked about the TAC (Thrust
Asymmetry Compensator) on the Boeing 777. I am working for Honeywell
FMS for Airbus.
I have some more questions on the Boeing 777. Please answer them when
you are free.
1) In any Airbus aircraft with the FBW Technology, as the aircraft
navigate, the FCC would automatically put appropriate trim to
compensate for the winds even if the aircraft is in the manual
mode of flying.
Is this feature available on the Boeing 777?
You mentioned that the TAC activates the rudder if it detects a
difference in thrust by more than 10% to balance the control
column. So in this scenario, what does TAC do? Is there
any system which take care of the winds?
2) In Airbus aircrafts, the Envelope Protection is Hard Type whereas
it
is Soft Type on the Boeing, i.e. Pilots make the decision to use
it or not.
(Like you had mentioned that the TAC can be over ridden by
pilots manually using the rudder).
The Alpha Protection Software for the Airbus A320 Aircraft limits the
AOA
up to to 30 degrees. So even if the pilot try to pull the side stick,
the on-board
FCC is going to limit it to 30 degrees.
How is the Envelope Protection taken care of on the Boeing 777? What
systems would interact and can pilots override the envelope if he
wants?
3) In the B747-400, you have single Auto Throttle Arm Switch in
the EFIS
panel. In the B777 there are two, L and R Auto Throttle Switches.
What makes the Difference?
4) In the Boeing 777 Electronic Checklist (operated by using CCD),
there are two line items, Open loop and the Closed loop which appears
differently in the MFD (Multifunction Display). Please update what is
that?
Big Questions? But I am sure you are the most
patient-and-answer-to-the-point pilot I have ever seen!
Please take your time to answer.
Thanks and Warm Regards,
Srihari J
Hi Srihari,
Wow... tough questions! I thought you ought to have directed
your queries
to the Boeing engineers! :-) Pilot's business is to fly
airplanes and
concentrate on need-to-know stuff rather than on nice-to-know
information. However, I will try to answer your questions with a
disclaimer that I am not an expert on technical matters as my Site
caters mainly for the curiosity of the average air traveler.
Here goes:-
(1) The Boeing 777 is automatically trimmed for a balanced flight when
the
TAC (Thrust Asymmetry Compensator) is in operation. With TAC on,
it will sense any imbalance due to an engine failure. It would
automatically add rudder pressure to minimize yaw when the thrust
level on one engine differs by 10 % or more from the other engine.
After a few seconds, the TAC applies sufficient rudder to make it
possible for the pilot or autopilot to center the control wheel.
To compensate for winds (I assume you are referring to its direction
of flight), even in manual mode, this is taken care of when the pilot
is on the TRACK SELECT mode.
(2) Envelope protection functions include stalling protection,, over
speed protection and roll envelope bank angle protection.
Stall protection limits the trimmed reference speed so that it is
inhibited
in the nose up direction. If speed decreases to the near stick
shaker
speed, the auto throttle will add power and thrust automatically.
For over speed protection, when the aircraft is at its maximum speed
(VMO/MMO), trim is inhibited in the nose down direction to prevent
over
speeding.
When airplane bank angle exceeds 35 degrees, the control wheel force
would automatically roll the plane within 30 degrees of bank.
All the above 3 protections can be manually overridden.
(3) On a Boeing 747-400, a single Auto throttle system moves all the
thrust levers to the selected reference thrust while the FMC commands
the EEC (Electronic Engine Control) to
trim each engine to equalize the thrust.
On a Boeing 777-200, there are two Auto throttle Arm Switches, one for
each engine so that each side can be separately selected on or off as
required.
(4) Closed Loop items are steps in the Electronic Check List that
involve
the continuous and automatic monitoring of switch, lever or selector
position. When the control is in the required position, the line
item text
color change from white to green.
Open loop items require the flight crew to manually confirm completion
by
using the CCD (Cursor Control Device) cursor select switch. It
does not provide any monitoring of control position or system state.
This can be distinguished from closed loop by display of the open loop
system indicator, a gray box located to the left of the line item.
The text color changes from white to green only when the pilot select
the CCD cursor switch.
Bye bye,
Regards,
Capt Kay
6.
Why aren't there on board video cameras on the Boeing 777?
Monday, June 24 04:31:37 2002
Hi,
The web site is the best there is! There is all the information
needed for a safe flight on the safest plane with the safest airline!
It is simply marvelous!!! I have a question for you. Why aren't there
onboard video cameras on planes? They would be in great help in case
of hijacking, wouldn't they?
Lyubomir Gunev
Bulgaria
Hi Gunev,
Thank you for the compliments
about my Web Site. I have been rather busy flying around to email
back. Regarding your concern about potential hijackings and
the installation of video cameras, all Airlines are in the process
of doing so in the future. Their main concern at the moment is
to prevent unauthorized entry to cockpit by having secured locks
fixed at the doors.
By April 2003, the doors must
be bullet-proofed and later on, video cameras would be installed.
It takes time to implement all the new security measures. In
fact, I have heard that the video cameras you talked about would
have the facility for the crew to identify suspicious passengers and
their pictures immediately beam to the ground (e.g. to the FBI ) to ascertain
their background.
These are just some of the
security measures for anti-hijacking that are in the process of
being implemented.
Bye bye and have a safe flight in
the future!
Regards,
Capt Kay
7.
What should I consider first if I want to be an airline pilot?
Thursday, June 27, 2002 1:37 PM
Dear Capt Kay,
I stumbled upon the web pages that you have created and found it to be
most informative and interesting. I am really grateful that you have
shared so many things that gave me so much insight to becoming a
pilot.
I am actually considering of becoming a commercial pilot. May I know
whether you have any specific advice on the factors that I should
consider first before deciding whether to be a pilot or not?
Please share your views.
CP Au
Hi CP Au,
So you are considering of becoming a Commercial Airline pilot? I
do get a
lot of questions on this topic. Here are some of my views.
Ultimately,
you would have to decide whether you want to make flying as a career.
Firstly, having flown for quite a number of years as an Airline pilot,
I
still find flying very interesting. (Ask John Travolta about
it!). Basically, to decide on a career, you must be happy with what
you do. As for me, I wouldn't be happy doing anything else.
It is a career that I find personally satisfying and financially
rewarding.
Flying an expensive machine (a new Boeing 777-200 cost around US$160
millions) from one point and landing safely at an oversea destination
is a fascination to many people. Your cockpit is your office and
you are on the move most of the times. You get to travel a lot
and meet many different people from all over the world. You are
like a CEO of a large Corporation but you have to shoulder a heavier
responsibility for hundred of lives are at stake if you ever make a
serious mistake.
Having painted a picture of some glamour that comes with the job, I
will now give you the other side of the profession. As an
International
Airline pilot, you would be away from home more than any other career.
It
can affect your family life and it takes a lot of understanding from
your
loved ones. You are expected to work during public holidays, at
odd hours
and fly through many different time zones but you have generous off
days,
leave and good fringe benefits. You may also miss attending your
closest
friend's wedding unless you are given sufficient warning. The
job is fairly
stressful for you are constantly being checked on your flying
proficiency
and medical fitness every 6 or 12 months.
So this career is not for everyone if you are the homely types or hate
travel. I have two personal friends who decided not to pursue
with their medical courses and went on to flying. Believe me,
both of them are flying as Captains today, one on the Boeing 777 with
me and the other one on the Airbus 330.
I hope you have some insight on the pros and cons about wanting to
become a Commercial Airline pilot now. The decision to be one is
all yours!
Regards,
Capt Kay.
8. Foul
air circulation on the Boeing 777?
Tuesday, July 2, 20:10:10
2002
Hi,
I have read that there have been problems on the Boeing 777's with
air circulation on long haul flights, causing nausea and fainting. Has
anything been done to alleviate this difficulty?
Thanks,
Debbie
Hi Debbie,
I believe you have read my FAQ on hazards
of long range flight regarding foul air in the cabin. So far,
I have not heard about whether Boeing has done anything to alleviate
the problem. Their explanation of the poor air quality was an
operational issue and not an oxygen problem and it is mainly related
to the control of the heat in the cabin.
I have done many long range flights of more
than 12 hours each on the Boeing 777 and have yet to receive a
real complaint about foul air in my flights. An United
spokeswoman said that people do get sick for various problems, but
not because of the poor air quality and they don't see any 'medical
effects' related to the Boeing 777.
Have a safe flight!
Thursday, July 11, 2002 3:56 PM
Dear Capt Kay,
I had a discussion with some colleagues regarding the cabin
pressure inside aircraft. I read on your web page about gunshots in an
aircraft and that the cabin pressure can be as low as 8.5 PSI (pounds
per square inch) under normal conditions. That is very low, almost
half atmospheric pressure.
Why doesn't Boeing (and other manufactures) build the air control
system in the cabin, so that it maintains atmospheric pressure? I know
it is technical possible to control pressures very precisely. And it
would be a lot more pleasant for passengers with weak ears or colds.
Thank you for a great web site.
Thomas Wolfe
Hi Thomas,
Although it is technically possible to build an air control system to
maintain an atmospheric pressure inside the cabin, the aircraft body
structure has to be redesigned to be very robust in order to withstand
the high differential pressures. In the end, the aircraft may be
too heavy to take off! (A submarine is designed to withstand
very strong differential pressures but look at its comparative weight
!)
Have a safe flight!
Capt Kay
10.
What is the difference between a Boeing 777-200 and a Boeing 777-236?
Friday, July 12, 2002 6:01 AM
Hi,
What is the difference between a Boeing 777-222 and Boeing 777-200 ?
Why does Boeing has many different planes such as Boeing 757-231 or
Boeing 747-446 ?
Regards
Patrick Raimond
Hi Patrick,
There is no difference between a Boeing
777-222 and Boeing 777-200. The last 2 digits refers to a
particular model of a particular Airline. For instance, from
my observation, all United Airlines Boeing 777-200's are Boeing
777-222, Delta Airlines are Boeing 777-232, Air France are Boeing
777-228, British Airways are Boeing 777-236 etc. This
applies to Boeing 757 or Boeing 747 as well.
Regards,
Tuesday, July 30, 2002 8:03 PM
Hi,
I have one question with reference to the basic climb performance of
a typical
Airliner like a Boeing 777. If you visualize the vertical view of
the climb profile of an aircraft, after takeoff and before the top
of descent I see a constant altitude segment. What is the exact
reason for it?
Is it because the Aircraft is under maximum gross weight and is
incapable of
reaching it's cruising altitude directly or is the pilot trying to
avoid a particular region so he needs to have a constant altitude
segment before cruise?
If you have a choice would you prefer to climb to the cruise
directly
or do you prefer to step-climb and why?
Thanks and Regards,
Srihari J
Hi Srihari,
It is not true to say a typical Boeing 777 profile has a constant
altitude
segment. Perhaps the profile you mentioned covers a short
sector of a
3-to-4 hours flight where further step-climbs have no economical
advantage. I do a lot of long haul flights from the Far East
to Europe of around 12 to 13 hours duration where there are at least
3 step-climbs. With a heavy aircraft (around 286,000 kg), the
computer calculates the optimum altitude of 31,000 feet initially.
As the aircraft climbs, the computers
recommends a step-climb to 35,000 feet when the aircraft weight
reduces as a result of fuel burnt (a Boeing 777 consumes around 6000
to 7000 kg of fuel per hour depending on the
weight).
Three quarter way through the flight
when the aircraft is about 55,000 kg lighter because of the fuel
consumed, the computer will recommend a further climb to 39,000
feet. Looking at this climb profile, it is not true to say
that a typical Boeing 777 has a flat segment from the top of climb
to the top of descent.
Pilots will rely on the Flight
Management Computer to choose the optimum level to climb to. If the
pilot fly at any level other than recommended, the airplane will
burn more fuel and hence uneconomical to cruise at.
When you mentioned about a constant altitude before cruise, I am
wondering if you are referring to the initial accelerating altitude
of 1000 feet or the 3000 feet (depending on the airport), which is
part of the noise abatement procedures.
Regards,
Capt Kay
12.
Will an airplane ditch safely on water?
Thursday, August 01, 2002 4:19 AM
Hi,
I have written and asked a question before and you replied very
promptly
and were very informative as in all your answers.
I read with great interest an answer that you gave someone about how
long
the aircraft stays afloat in the event of a water based landing. I
must say,
I have often wondered if it was possible to do this (as anyone who
looks
down and sees water as far as the eye can see probably does!).
What I would like to know is, how is this performed? Above all, in
terms of
landing speed, weight, angle of descent, attitude and inclination
etc, how
is it possible to execute such a landing when you will surely
encounter a
great deal of resistance from the water surface on final touchdown,
at what I
assume would be just above stalling speed?
As the landing gear would not be down, I would perhaps guess that it
would
be the engines that touch the water first. Would this not cause a
sudden
jolt forward along with a dramatic reduction in speed that could
damage the
structure of the aircraft?
Is this part of simulator training?
I would be very interested to know the answer to these questions.
Thank you in advance, keep up the great site and happy flying.
Robert Hirons,
Marseille, France.
Hi Robert,
To answer your question, firstly, have you ever seen an amphibious
airplane
landing on water - if not in real life or at least in movies?
Okay, those
airplanes were specially designed to do so on fairly calm waters and
into
wind. So it is possible for an airplane to 'land' on water,
don't you
agree?
Now the question is how well will other non-amphibious airplanes
perform in a ditching? Many factors must be taken into account
as I have mentioned in my previous FAQ. Some years ago, an
African Airline Boeing 757 ditched into sea when it ran out of fuel
after being hijacked. I personally saw it on the CNN News.
Somehow, it was not well executed because one of its wings hit the
water first. It cart-wheeled and broke up but there were some
survivors.
What I want to say is that, it is possible to ditch safely if all
the conditions are favorable. Similarly, if all the prevailing
flying conditions are non-existence, even a crash landing on the
runway or land surface would be disastrous!
In a well executed ditching, the airplane must be controlled at the
recommended landing speed for its weight just like a crash landing
(see my
FAQ on landing with loss of all engines - where an Airbus 330
crashed
landed safely). In a perfect ditching, the rear belly contact
water first
before the engines. It is true that there would be a great
deal of resistance from the water surface on final touch down.
As you rightly said, the landing gears should not be down -
for that would cause an even greater drag from the water surface.
Damage to the structure of the airplane would be inevitable if the
contact speed is excessive or if the wings were not level on impact
- just like what happened to the hijacked Boeing 757 above.
In the simulator training, flight crew have been trained on all the
procedures for executing a safe ditching at sea but in real life, he
needs
all the favorable conditions to exist - just like some people need
luck to
survive a car accident!
Have a safe flight always!
Capt Kay