dear friends followers welcome back to
my channel and to a very important topic
you are most likely going to mess up at
least once in your pilot career descent
planning how does a pilot know when to
initiate his descent towards its
destination aerodrome this is today's
question so I'll show you a few thumb
rules which will make your descent a lot
easier and avoid coming in hot and high
so get your brain ready for some easy
head calculations and let's get started
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this is undeniably one of the procedures
every pilot messes up at least once in
his pilot career the descent planning
tell me about it transitioning on to the
Boeing 747 which is heavy as lead and
fast as a bullet will slap you in the
face if you think you can fly her like
an airbus a320 which has a glide ratio
comparable to a flying piano once you
extend to speed breaks there is only
little room to play with once you fly a
wide-body airplane but how is it done ok
the times where you flew inbound to your
destination Airport and just look
outside of the window and then decided
to send visually towards the runway are
over at least within the airline
industry now you might have seen these
abbreviations and videos about a
navigation display this shows the top of
descent point in regards to the entered
flight plan in the FM GS on Airbus
models or on the F and s on the Boeing
obviously this is a great help showing
you when to start your descent but there
is a big flaw with that top of the send
point on the nd and I'll show you in an
example why and why it is important to
me that you know a few thumb rules to
not mess up your approach now let's
assume we're approaching into Hamburg
Germany now we've got the approach set
up but as you see here on those two n DS
the top of the sent points are at
different locations how can that be
now this nd shows a direct approach
towards from a3 3 and the other includes
a so called transition I
transition is an approach procedure in
order to slow down the incoming traffic
and makes it easier for the approach
controller to stack the planes or as
they say pushing tin before handing them
over to the tower controller so with a
transition the flight or approach
distance moves the top of descent to a
later point compared to a direct
approach which will want you to descend
earlier as you only have a certain
distance left over this makes sense
right compare it as if you were driving
to your girlfriend's house and she wants
you to call her 30 miles prior reaching
her house to get dinner ready now you
are on a direct route but let's say you
need to perform a little detour or a
transition at your ex-girlfriends house
that will move your time of call or top
of descend to a later point right so in
order to anticipate that the controller
might take you in for a direct approach
always plan with the shortest distance
to the runway now the easiest way of
finding out the distance to the airport
is by tuning in the closest vor/dme to
the runway you are flying to so in our
case Hamburg has a DME station named
Ulster right at the airport so we're
going to be tuning in ulster alpha Lima
Foxtrot and will give us a distance of
now as you see on the PFD and nd we're
at 27,000 feet with a speed of 320 knots
and a tailwind of 20 knots
let's neck wait for of the plane for a
moment so with that data we want to
calculate the distance we need to fly a
continuous descent profile so the first
thing we're going to look at is the
altitude we're gonna have to lose now
Hamburg is at 53 feet above sea level we
can disregard that and so we effectively
have to descend 27,000 feet now keep in
mind if your destination Airport is
Bogota for example you would have less
altitude to lose as the airport already
is at eight thousand three hundred feet
so we're going to cross out the last
digit
and divide that by 3 so 270 divided by 3
equals 90 so 90 nautical miles is the
minimum distance we'll need for our
descent
now the next factor to consider is speed
as there is no way that we'll be landing
the plane at 320 knots now we'll
consider 200 knots as an average to send
speed as you are progressively getting
slower over the entire descent profile
including company speed restrictions
like 250 knots below 10,000 feet but
I'll come back to that in a minute so
we've got to lose a hundred and twenty
knots indicated air speed not ground
speed and a good estimate for most plane
is one nautical mile per 10 knots speed
reduction so a hundred and twenty knots
divided by 10 equals 12 nautical miles
to reduce to speed last but definitely
not least and often forgotten but easily
messes up your descent planning is the
wind now in our example we have a
tailwind which will make it harder for
you to lose altitude and kill speed so
for every 10 knots of wind you add one
nautical mile so we have 20 knots
divided by 10 equals 2 nautical miles we
have to add to our mileage now if it
were to be a headwind you subtract a
miles
Capisce so summing up our calculations
we should be starting our descent at a
hundred and four track miles as you are
in descent you want to check every
10,000 feet if you're still on the
correct vertical profile and then
decrease or increase your vertical speed
speaking of vertical speed there is
another technique you can apply now
we'll use 200 knots as an average
descent speed as mentioned previously so
we've determined the distance needed of
a hundred and four nautical miles so for
easy calculations let's say a hundred
nautical miles that means you need 30
minutes for the entire distance 27,000
feet divided by 30 minutes equals 900
feet per minute which would be your
average vertical speed I'm personally
not
vertical speed flyer and I'll tell you
why first of all 900 feet per minute is
in most cases not steep enough for the
initial descent and the controller will
be faffing about why you're descending
at such slow rate in the rarest cases
the vertical profile is a 3-degree glide
slope from top to bottom as it is she
impossible to maintain that slope and
reduce speed at the same time compare it
as if you were coasting downhill a
highway at 60 miles if you wanted to
slow down but you couldn't use the
brakes
how would you slow down the only way of
doing that is if the highway would
become shallower so commonly pilots
start off with a high-speed descent at 3
degrees or steeper now just before
reaching 10,000 feet you dial down the
speed the plane pitches upwards creating
a shallower descent path equal to a
thousand feet per 5 nautical miles now
once you receive further descent
clearance you rejoined a 3 degree angle
equal to 1,000 feet vertically needing 3
nautical miles horizontally maintain 250
knots until reaching 5,000 feet down to
speed even more so you can extend the
slats and flaps to establish yourself on
the ILS VOR approach etc so your
vertical profile is going to look
something similar to this now once
established on the approach another
thumb rule ground speed times 5 gives
you the necessary vertical speed feet
per minute you want to be flying to
maintain on the 3-degree glide slope but
for descent I primarily use the first 3
thumb rules I've mentioned and your goal
should be as it is mine to fly the
entire descent on idle power and only
apply thrust after the final flap
setting the least efficient thing you
can do is if you use the speed brakes
for the descent and then you have to
apply for us to maintain altitude before
reaching the glide slope you've then
killed kinetic energy for no good reason
that's the point I'm at right now with
the Queen so
she's still testing me well I have to
admit that sometimes we land with the
maximum landing weight and the next day
we land with a hundred tons less and
that for sure has an impact on the
handling and descent characteristics of
the plane let's look at a scenario which
is quite common the controller won't
give you the descent clearance due to
traffic crossing at lower levels so you
slowly get over your descent profile now
what's now there are three things you
can do to rejoin your profile once you
have your descent clearance increase
speed and idle power dial up the speed
and pull back the thrust levers and the
autopilot immediately will try to
capture the speed but without Frost now
the only way of doing this is by
pitching down so you and your passengers
will feel that descent believe me but
it's fun though try to get below your
descent profile as quickly as possible
as that will give you space and time to
slow down the airplane again
now if ATC advises you to maintain a
certain speed which is too slow to kill
altitude use your speed brakes the air
brakes or high drag devices whatever the
manufacturer named them that's what they
are made for a video about that topic is
coming up soon now remember the car
scenario I've mentioned before now you
are allowed to use the brakes actually
to slow down a you might even use the
gear or flaps but you most likely not
going to retract and once you've used
them and the last resort ask for delay
vectors or more track miles you ever so
often hear colleagues ask the controller
how many track miles can we expect and
he'll respond let's say 25 nautical
miles the pilots quickly do their
calculations and if they're too high
they'll say unable request delay vectors
so the controller will extend their
downwind for example to give them more
time to lose altitude or reduce speed
now you might say Joe this is all nice
to know but I'll rather rely on the data
I've put into the F MGS or FM s and I
use all the help given on the navigation
display that's fine by me
but the
fermez and all the other help cannot
anticipate a sudden direct approach
given by the controller and if you're
replying unable we're too high for the
approach you'll be the reason for many
smiley faces in surrounding cockpits and
they'll be happy to Nick your slot for
the approach so fly conservative but
also plan ahead constantly monitor your
distance to the airport and if necessary
use the speed brakes or extend the flaps
or even the gear to lose speed and
altitude as always situational awareness
is key you'll get a feel for it don't
worry also on how to anticipate the
surrounding traffic and the mood of the
air traffic controller a go around cuz
you're hot and high might happen as
you're unable to establish yourself on
the approach but it's not a failure it's
more of a lesson and you'll profit from
that's it for today thank you very much
for your time to become my wingman hit
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upcoming videos and don't forget a good
pilot is always learning see you next
week always
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