Is your B737-800 Cat C or D?
 

Is your B737-800 Cat C or D?

Playing around the other day and basically the 73-8 seems borderline on whether it is cat C or cat D due to higher threshold speeds.

What cat is yours?

Category is based on threshold speed which calculated by:

Stallling speed in landing config at max landing weight X 1.3

Under FAA regs you can go up a category but you cannot go down one.

But it seems some regulations allow you to dispatch at different weights to give you different categories.

Our books say that they are Cat C full stop even though often the limiting speeds are exceeded... Intruiging, I shall ask around ;)

Realistically, its Cat D...based on 1.3 and other issues not as apparent.
Try hitting 140kts at the FAF with flaps 15.....

Note 140kts is the final approach speed for Cat C


http://www.faa.gov/documentLibrary/m...ND/8260_52.pdf

Is it possible that the formula for TAS is wrong?
 

Or maybe the explanation in 1.11.1 is wrong:

VKTAS = VKIAS × [1+ (altitude× 0.00002)]
Where V = Indicated Airspeed
altitude = Maximum segment altitude in thousands of feet

For 200 knots at 30000 ft:
200 x [1 + (30 x 0.00002)] = 200.12 knots, hardly any difference at all.

Should that be feet instead?

Yes, In simple terms just add 2% of IAS per 1000ft. Much easier?

The calc is used in true airspeed for the turn radius and bank angle calcs, which is the arithmetical way of extrapolating out the ground distance (which the design programs use) vs the air distance at altitude with respect to the curvature of the earth....


(see the crap we have to deal with)

sorry, to answer your question, you are correct, its written poorly, its in feet, so 1500 isnt 1.5, its 1500, as it seems to state)

also, there are several significant addendum to this root document...so this doc is not entirely accurate. (good catch)

The FAA reg apparently requires a minimum of 1.23 Vso. I've read it, don't have the time to search for it right now.

737-800 Flaps 40 uses 1.25 Vref. Don't take my word for it, do the math vs. the stall speeds in your performance manual. I originally saw the 1.25 Vso explaination on pprune and verified it using our performance manuals.

Stall speeds Flaps 30 vs. Flaps 40 is 2 kts. Vref difference is 7 kts. The 1.3 Vso for Flaps 30 vs 1.25 Vso for Flaps 40 explains the Vref difference.

Is this mixing definitions? My perspective was from procedure design determinations for individual segments.

The Class determinations are in the .52....

Note the 140 kts is max speed for the Final segment for Class C.

The 747-800 is much more likely Class D or even E depending on loading/config.

With regards to Vso, what is shown on the indicator is based on max landing weights, if this is used when light, one will go long....perhaps the 1.23 min you are referencing is in these regards...

FlightpathOBN - on jet aircraft there is nothing 'shown on the indicator' about the aircraft's stall speed. I've only seen that on small aircraft's airspeed indicators.

Can't remember all the figures, but memory seems to be that CAT C on 2 engines and CAT D possibly on 1. With all that arithmetic flying around perhaps someone has the answer.

misd-again, yes...I got that indicator one sideways..

With the .52 designs, the 140kts is for the entire final section, typically at least a 5nm segment....so if you have a turn that ends at the FAF, the curve is designed with 140 +winds, so one can start to see how difficult it is to get an 800 to 140kts 8 or 9nm out....and who wants to....

I know that quite a few procedures have been re-worked that were originally designed with the 737-400, and the 7/8/900 series just cant make the turns with stab flight.

Boeing has specifically answered this question to our airlines query and said that our 738s are to be considered Cat C irrespective of the approach speed being in Cat D for certain approaches .

CAT C for Straight in CAT D for..... This is in the FCTM 5.......
If you work out the speeds from QRH PI.... and the definitions from the AFM you will find out that is D by 2kts.
If you are asking myself i will tell you that is D, but if you ask Mr Boeing they will tell you..... :cool:

What's Category A,B,C,D mean?

Jane, Robyn... it has to do with 'circling' approaches where on an instrument approach you have to reverse course to land on the opposite rwy...I'm trying to find a picture...:)


• Category A: Speed less than 91 knots.
• Category B: Speed 91 knots or more but less than
121 knots.
• Category C: Speed 121 knots or more but less
than 141 knots.
• Category D: Speed 141 knots or more but less
than 166 knots.
• Category E: Speed 166 knots or more.
http://www.faa.gov/library/manuals/a...ection%20I.pdf

see -page 32 note other pattern are possible those just serve as some examples...most airlines these days either avoid the procedure entirely or limit them to day visual meteorological conditions

Pugilistic Animus

Understood.

I assume Concorde (when it flew), the MD-11, and B-747 at high landing weights would fit into Category E?

I would guess those to be Cat E but I don't know..[circling with Concorde:\....
it is important to remember [for example] that even if the approach speed is slower then the minimum for a category-i.e at low weights---you still must use the certified landing category.
i.e if the MD-11 is light and the actual speed is below CAT E--you still must use CAT-E minimums---


and with the MD-11 I think that it competes with the SR71 in terms of Vref---it's a CAT F ship...:}:ouch:

From my company's POM:-

For Instrument approaches we are Category C.

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

What would happen with airport access if the 737 were re-classed to D?