Egine Fail Height Vs RVR/VIS ????

[PorcoRosso]

How do you use this table ? It deals with JAR-OPS 1, A/D operating minimas

Example :

Engine Fail Height_________RVR/Vis
<50 ft___________________200 m
51-100__________________300 m
101-150_________________400 m
(..)
>300____________________1500 m

Can't get a clue how & when to use it ...Flight planning ?

What does it mean ? You are not allowed to loose an engine below 100 Ft if your RVR is less than 300 m ...Confusing

Best Regards

[BizJetJock]

If you are in a performance class B aeroplane (small props mainly), there may be a height below which an engine failure requires you to land straight ahead even if there is insufficient runway. Typically this is the point where the u/c has fully retracted. If this is the case then for planning purposes you must assume an engine failure at that point, and your RVR for takeoff is limited according to the table you are referring to. In class A aeroplanes (all jets and turboprops >5700kg) you assume the engine fails at V1 on the runway and there is a separate table of RVR against runway markings/lights since it's all about keeping straight on the ground before liftoff.
Hope this helps.

[PorcoRosso]

Bonjour BJJ, sorry but am still a bit confused about the way to use this table.
On which criteria do you select an height to find the associated RVR ?
How do you decide of your assumed engine fail height ?

[BizJetJock]

You have two choices for selection of engine fail height on performance class B aircraft. On the day you can use the actual cloudbase (the wording is "at the point of loss of visual reference") and work out the engine out path from there. Alternatively, and more commonly, at the planning stage you use the lowest height that your aircraft can climb away from (usually gear up and locked) from the AFM. When you're talking about heights less than a few hundred feet, you have the same scenario as on an approach, that you may well have runway/ lights visible when you are below the formal cloudbase. Therefore they give you a table (similar to the ones for minmum RVR for landing) detailing the minimum vis for takeoff. This table applies to all performance categories, but since class A aircraft (all jets and turboprops >5700kg/9 seats) are required to cope with an engine failure on the runway at V1, only the first line applies, giving a minimum vis of 200m. (unless, of course your company is approved for Cat II or III ops, when different rules apply).

Hope this helps!
BJJ

[eyeinthesky]

Further to BJJ's explanation:

Think of it as your insurance policy. As highlighted, some aircraft are not guaranteed to achieve minimum climb gradients with an engine failed until, for example, gear and flaps are retracted and the failed engine is feathered. You can derive this from the performance graphs for the aircraft type.

If the aircraft is not able to climb above obstacles, you are committed to landing, and you must have sufficient visual reference to achieve this. It would be a risky manouvre to depart into a 50ft cloudbase, lose an engine and be unable to climb, then be forced to try to land with an RVR of 200m!

Thus, the height at which the aircraft can deal with the failure and achieve an obstacle-clearing climb gradient becomes the number you use to set a minimum RVR for take off.

An example:

One of the aircraft I fly has a worse climb performance with flaps extended than with them retracted, and the flaps are not always needed for take-off. So in the case of an engine failure it can climb away without flaps extended from a lower height than it can with them extended. Therefore, the minimum flapless RVR is 300m, but with flaps it is 500m.

Another aircraft made by the same manufacturer but with one less engine can achieve the same climb gradient irrespective of flaps extended or retracted. Therefore the RVR for that type is 300m.

As for when you use these minima, the answer is whenever you take off. They should be written into your Ops Manual and you lay yourself open to investigation by the CAA if someone reports you departing with an RVR lower than the minimum allowed.

All of this is of course under public transport rules. If you are non public-transport, then the aerodrome minima apply (these are usually lower), but the risk for you remains the same if your donkey quits at 50ft...

[PorcoRosso]

Thank you guys !

I think I have the picture now
Why don't they give examples like that in the JAR-OPS documentation ?

Best regards