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andreadebiase

Approach category and REF speed question

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If i understand this correctly an approach category D is such when landing between 141 and 164 knots (correct?), but is that referring to the REF speed or the actual flight speed which is REF +5?  example: if my REF is 139 I am a C but if i set the speed to 144 (139+5) am I a D or still C?

 

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Hi Andrea,

 

It's much simpler than that - the aircraft category is determined by Vref (strictly, Vat) at MLW, not the weight on the day. I'm fairly sure the NG will be Cat C but I'm not familiar enough with the type to say with certainty if that's true for all variants.

 

Edit to add: the above is true for ICAO/PANS-OPS procedures. Procedures designed under the US TERPS rules are slightly different and don't protect the same amount of airspace for circling maneuvers, so if you are circling on a TERPS procedure at a speed above that for the category the aircraft would otherwise be in then you must use the minima for the higher category (but you cannot use lower minima if you happen to be circling at a lower speed than that the aircraft is normally in).

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What determines an aircraft category which it falls in is vat or vref over the threshold. So aslong as you are between 121-140kts OVER the threshold you are CAT C.

 

So if you are doing 180kts During a circling approach, you are still not CAT D because your vref speed over the threshold will be CAT C.

 

This is what i use from my POM;

 

For Instrument approaches we are Category C.

 

For Circling approaches we are Category D (FAA), but Category C (ICAO)

 

I have the airfield brief for LOWS and in the part CIRCLING RWY 33, it mentions...

 

NOTE; When the reported crosswind exceeds 10 kts, CAT D Circling minima must be used.

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Keep in mind that in the FAA, if you have to fly at a speed in excess of the certified category, you must operate at the higher category minimums. Circling is a good example and landing in an abnormal configuration is another. It's all about the protected area and keeping you from killing yourself and others. The U.S. has had a history of having dangerously narrow circling areas. TERPS standards are better now, but some procedures have not changed. Just remember that this protection goes from approach up through missed approach. It's imperative to know and understand your aircraft category, circling capability and what protection it affords.

Rick

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Correct rick just the same as flap malfunction for an example. Your aircraft is CAT C and thats fixed by a said operator and cannot be changed, but that doesn't say you as a pilot can't make a sound judgment and use CAT D CIRCLING minima because of the higher speed due to flap malfunction

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Hi,

 

I have just found by chance a document from Boeing called "Airport Reference Code and Approach Speeds for Boeing Airplanes".
In this document, the B737-800 and upward are classified cat D for approach.

I'm not sure I'm allowed to post the link to that doc, so I just leave.

An evidence that contrary to what we may logically expect, the approach speed has nothing to do with the aircraft size (we may think the bigger the faster), but according to that document, B738 and B739 are cat D along with B753 and B767, but B772 and B77L are cat C.

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Hi,

 

I have just found by chance a document from Boeing called "Airport Reference Code and Approach Speeds for Boeing Airplanes".

In this document, the B737-800 and upward are classified cat D for approach.

I'm not sure I'm allowed to post the link to that doc, so I just leave.

 

An evidence that contrary to what we may logically expect, the approach speed has nothing to do with the aircraft size (we may think the bigger the faster), but according to that document, B738 and B739 are cat D along with B753 and B767, but B772 and B77L are cat C.

 

That might make a little sense on the surface, but keep in mind that this is for airport and procedure planning. This isn't for how pilots should, or generally operate the aircraft. The document you found essentially provides the "worst" possible case scenario for the procedure and airport planner to design to. That way, if you plan to the given values, you are also planning for the more common and less common scenarios simultaneously.

 

As Rick mentioned, simply look at the speed table, select a category, and use the values on the approach chart for that category.

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Hi, 

 

Thanks for the clarification. 

However, there is still something that gets me confused: According to what I have read about the approach categories, they are based on the Vat at MLW, so not dependent on the actual weight of the aircraft (except for the circling if I understand correctly). However, I'm not so sure when reading the posts above on what we must refer when select a minimum for an approach: still the MLW or the actual weight?

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However, I'm not so sure when reading the posts above on what we must refer when select a minimum for an approach: still the MLW or the actual weight?

 

Think of it this way:

 

Approaches are designed with specific radii of protection in nautical miles. If you are going faster, you will reach that limit of protection faster. As such, would you base your category on how fast you're theoretically flying, or how fast you're actually flying?

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Well that make sense, I would logically choose the minimum corresponding to my actual Vref, but what is sensible and what regulations say don't necessarily match!  :wink:

So I guess the approach category of the aircraft (based on her MLW according to the definition) and the approach categary "used" by the pilot to choose the minimum are not necessarily the same.
 

However, can a pilot choose a minimum that corresponds to a category lower that the certified one of the aircraft? I mean a B77W is cat D at MLW but an empty may have a Vref corresponding to cat C. In that case, is the pilot allowed to choose a minimum corresponding to cat C or must the choice of the minima be conservative and keep cat D?

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However, can a pilot choose a minimum that corresponds to a category lower that the certified one of the aircraft? I mean a B77W is cat D at MLW but an empty may have a Vref corresponding to cat C. In that case, is the pilot allowed to choose a minimum corresponding to cat C or must the choice of the minima be conservative and keep cat D?

 

It's not like you communicate your category selection on freq, or always have a fed looking over your shoulder...

 

...so, yes.

 

Even so, I don't think anyone would fault you for choosing the more conservative option from a regulatory perspective. Diverting to another airport because you chose Cat D over Cat C when you were clearly Cat C might get you into hot water with your operator.

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Hi, 

 

Thanks for the clarification. 

However, there is still something that gets me confused: According to what I have read about the approach categories, they are based on the Vat at MLW, so not dependent on the actual weight of the aircraft (except for the circling if I understand correctly). However, I'm not so sure when reading the posts above on what we must refer when select a minimum for an approach: still the MLW or the actual weight?

 

I got a great reply not long back so i'll share -

 

I believe the 737-800 is CAT C, at least in europe. However, the 900 seems to be in Class D. In a non normal case you might be better off using CAT D minima though as flaps 15 in a fail passive airplanes is the usual non normal configuration (fail operational ones can still use flaps 30 single engine and flaps 30 is required for autoland). However that isn't required by SOPs as far as i'm aware, but is rather a "technique" or "airmanship" item.

 

The 900 seems to be CAT D, which is actually in line with the A321 as the stretched variant that is CAT D as well, whereas the smaller ones are CAT C.

 

Hope thats helps...

An evidence that contrary to what we may logically expect, the approach speed has nothing to do with the aircraft size (we may think the bigger the faster), but according to that document, B738 and B739 are cat D along with B753 and B767, but B772 and B77L are cat C.

 

CAT C for all 738s, same as on the 700. I believe that is the case in all of EASA land, however it is apparently the reason that flaps 15 cannot be used as normal landing flap setting, only as non normal one. flaps 15 is allowed as normal flaps setting under FAA rule. However think the FAA only allows switching from C to D!

 

If landing at max LW on a 739 at f40 vref will be 142 kts (above 141) hence 900 are CAT D normally. In that scenario with a LDW of 60t and vref lets say 135, you are still a CAT D

 

If you fly an approach on a cat C 800, you have flaps problem and your Vref is now above 141, then as PIC you may use higher minima CAT D.

There are max speed for circling and intermediate missed approach for each "category" and should be reviewed in NN conditions.

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