A-320 Dual Engine Failure

[Jimmy Hoffa Rocks]

If you have a A-320 Dual Engine Failure- No FUEL- no relight.

Does anyone have rules of thumb for calculation the glide ratio
-distance and height

Of course depending on weight and winds,etc

Profile

But say at 60T

Any tips on the dual engine failure procedure.Appreciated.

Like when do you leave the ECAM to go to the QRH ?

Thanks,

[Pro Spin]

Jimmy

When you have confirmed that there is no fuel remaining and reset the FAC to get back the characteristic speeds, pilot flying should select green dot speed which will give an approximate glide ratio of 2.5nm per 1000ft (no wind). Weight doesn't affect glide ratio in still air.

So, at a cruise altitude of 38,000ft you can glide for about 95nm still air. Remember though that you need to configure the aircraft before landing which will hugely affect the glide ratio (gear and flap), also you'll need to position yourself for the landing runway which may not be straight in, so you'll need to take off about 5-10 miles for those.

As a tip, when Pilot Flying (from Left hand seat as F/O loses their PFD and ND), I always select the ND to NAV mode 180nm range straight away as this gives you a 90nm range all around the aircraft to select the best airport for an emergency landing (as the best might be behind you!)

The Eng Dual Failure drill should be completed from the QRH immediately and not from ECAM.

Hope this helps.

Pro Spin

[aulglarse]

read the small print when fully configured on approach. QRH says aprox 800ft per nm which is 2-1/2 times greater, than normal(320ft/nm)profile. For example, holding 140kts on final usually holds 700ft/min. In this scenario this equates to 1750ft/min:uhoh:

Don't get low I suppose.

[hawker750]

Quote:
Weight doesn't affect glide ratio in still air.

For a given IAS a heavier aircraft will have a lower ROD so surely weight will affect glide ratio (by not very much).

[Permafrost_ATPL]

At constant IAS, distance will be greater for heavier aircraft indeed. But you should fly as close as possible to best L/D ration, which will give a constant glide distance regardless of weight (ignoring very minor IAS compression factors).

P

[hawker750]

Permafrost,
I do not think you are correct. A heavier aircraft has a greater potential energy. Potential energy = thrust so regardless of L/D a heavier aircraft is like have a bit of thrust available. It is just physics

[OPEN DES]

Permafrost is right.
Best L/D ratio is a property of the airfoil, just that. Weight does not influence the best L/D ratio; you'll just find at a different speed.
Provided you fly at best L/D ratio speed (green dot when OEI) your descent gradient is the same at all weights.

However:
In normal ops (flying let's say 290 kt for descent) we will have a worse L/D ratio at low weight (so a worse gradient) because we have a larger margin to green-dot/best 'L/D' ratio than with a higher weight. Hence the common misconception that a lighter aircraft will descend more rapidly than a heavier one; this is only the case when flying fixed speeds for descent (or a ECON speed for that matter).

[hawker750]

I disagree. A heavier aircraft will need a higher IAS to have the optimum L/D and will have the same ROD as a lighter aircraft. A higher IAS means it will go further.
If I am wrong where does the extra energy go?
You will be telling me next that a heavy aircraft takes the same energy to climb to a particular altitude as a light one because L/D is only a factor of the aerofoil

[OPEN DES]

Yes you are wrong.
Best L/D ratio is only a function of the airfoil! Best L/D ratio defines the best gradient. To achieve best L/D ratio a heavier a/c will need to fly at a higher speed. Ofcourse this higher speed comes with a higher ROD than with the lighter aircraft but the resulting gradient is identical. The heavier A/C will fly faster and hit the ground first, but at exactly the same spot as its lighter weight counterpart.
What happens with the extra energy of the heavier aircraft? Well the heavier aircraft will need more lift and this extra lift will give more induced drag, and also more parasite drag as a function of the increased speed.
The Lift/Drag curve for a heavier weight a/c moves with its best L/D point moving along from a line starting in the origin of the graph.

the QRH gives a glide ratio for green-dot at 2.5NM/1000ft. This equates to 400ft/NM. This is directly proportional to the L/D ratio of this airfoil at any weight in this specific config.


You will be telling me next that a heavy aircraft takes the same energy to climb to a particular altitude as a light one because L/D is only a factor of the aerofoil
This is were thrust comes into the equation.....


What we see on the line is that a lighter aircraft will descend steeper than a heavier one. This is because we don't fly the same L/D ratios. When flying 300knots in a 70t a/c we will have a better gradient than at 60t because at 70t and 300kt we will be closer to the green-dot (=best L/D) for that specific weight. Even ECON/managed descent speeds for different weights do not have the same L/D ratio. Unless they had the same factor over its respective green-dot.

[NigelOnDraft]

The heavier A/C will fly faster and hit the ground first, but at exactly the same spot as its lighter weight counterpartMaybe... but only in still air ;)

NoD