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?

Don't throw the 700 in there, it is usually a lot slower during approach than the classic (300/400/500). Vrefs are quite often around 120kts whereas the 800 has them more around 140. I have done approaches with a Vref as low as 112 kts in the 700 which can be quite embarassing compared to all the other traffic around.

The Vref at Flaps 40 at MLW 66.360 kg is more then 140 kts. But that is only to decrease the ptich to avoid tail strikes in the flare. Even more visible when comparing the Vref´s of Flaps 30 and Flaps 40. Difference is around 7 kts on the 800 and only around 3-4 kts on the 700. So basically the Vref of the 800 is around 1.4 VS due to the facts mentioned above, thats also why turning with more then 15* bank in the lower yellow hollow bar is no big deal aerodynamically. (but then again commonality to the classic would be lost..) It is for sure on the 400.
So to get back to the subject, if VS 1.3 is taken then it would be easily under 140 kts, making it Cat C.

Regards repulo

Thats all good...except, if you look at procedure design, then the entire final segment max speed is 140kts, or as you say flaps 40...you want to fly the last 5nm at flaps 40

That would make it easy to achieve the 1000ft gate, after all we still have to run our checks after we have final configuration. I have no problem with flying 5NM at final config, we need around that anyway.

We had the same dilema. And the solution was rather simple:
MLM= 64999 Kg --- and Caa was informed and aproved this.
Also we were asked to use flaps 40 in order to keep Vref below 141 Kt when flaps 30 would require a Vref above 141 Kt.
Given all this consideration we operated 737-800 for cat C.

Hope it helps...

Yes, these are all solutions, but it takes some getting used to, from an operations and a procedure design.

With RNP, I usually have a transition turn to final. The criteria wants the turn to be at the final segment speed as well, so if you have a 3 nm radius turn, that will be 4nm long, this puts that final CAT C speed of 140kts now back 9nm. We also have to remember this using a 3 degree GPA with idle descent.

If one uses the criteria, at 140 kts, a 2nm turn is possible with the 25 degree bank limit. There are many procedures out there, such as Palm Springs, designed this way. Getting to final config, rolling through a turn like this, was just too tough to accomplish consistently with the 7/8/9 winglet models....and these were very experienced operators.

Hope that clarifies my perspective is on this topic.

As far as I remember : "an aircraft shall fit ONLY ONE CATEGORY"

Concur, but as for performance, would you consider a 737-200 and a 737-800 the same?

FlightPathOBN

Do you mean the same performance as the B-737/400 and the B-737/800 ??? Yes indeed !!! Cat C and that's all no more doubts or conclusions.

Yes, and this worked great when it was written in 1953....

here we go again....:D

our 700 are C and the 800 D

737ng...

I am glad that your group has decided to differentiate the models...it is far more satisfying to design procedures that will actually be used, and have value, without the pilot saying WTF...

than a 30 year old criteria...

mvsb1863:

The 727-200 was C straight-in and D circling for the many years I flew it.

Today, the bigger Gulfstreams are C for straight-in below a certain weight; D straight-in above that weight. They were certified that way.

One word (category) different meaning and context.
 

For manufacturing certification purposes an aircraft will only fit into one approach speed category based on (already noted) 1.3 times the stall speed in the landing configuration at maximum gross landing weight.

Now place ourselves in the cockpit flying the Boeing 737-800 after a maximum weight takeoff and we need to return for landing under instrument conditions on one engine and no flaps or we need to divert to a nearby alternate and must to circle to landing (not our day; the engine failure damaged and jammed the flaps) and somebody asks “What category minimums do we use?” It is the same word, category, but now this becomes a practical application issue. We are going to use the approach category for the speed we are actually flying and not the Category C minimums the aircraft was certified as. We are having a different discussion and no longer talking about certification. [For the sake of brevity I am skipping the discussion related declaring an emergency and doing what necessary to land safely and no longer being bound by the “regulations”].

There may be a case where an operator may further limit themselves and require their crews to use the more restrictive minimums say Category D at a particular airport. This now becomes company policy and dispatch decision and not a certification nor a practical application issue.

When this question comes up we need to clarify what context we are discussing approach categories. Are we discussing approach categories in relation to manufacturing certification, line flying application under different circumstances or self imposed operational company policy and dispatch requirements? It is possible to have different answers and each is correct.

For certification purposes our -800s are Category C.

yes, I see the discussion wandered between regulations and reality...

I believe the original design parameters are 1.3, flaps 15, at the 5nm FAF, hence my issue with the certification.

(I meant design parameters, not cert parameters)

Our 737 are certified as cat C, however we do fly them as C for straight in and D for circling approaches. Did the same for our classics (all 3 variants) and now even the 700 although it is by far slower than any classic or the larger NGs and should easily fit into C for all applications even in real flight ops.

I've seen a few posts say what the "regs" say, but no-one has actually posted or quoted the actual regulation that defines the categories.

Can I suggest Part 97, Section 97.3:

Note that the 1.3 times stall speed only applies if VREF is not defined - since I'm pretty sure the 737 has an explicitly defined VREF, that's what counts, not some arbitrary factor of stall speed. (Which makes sense, after all, it's what you're being told to fly).

This is the resultant classifications, but Vref refers to Flaps 30, max landing weight, no thrust.
The other Vref's, such as Vref20, etc are just that flaps 20.

Due to your aircraft configuration, the Vref will be somewhat variable.

747-400 Operating Procedures Manual
MLW of 297,500Kg (654,500Lbs).
Reference speed for each flap is follows :
Minimum Clean Vref + 100Kias.. 136+100 = 236 Kias
Flap 0............ Vref + 80 Kias...136+80 = 216 Kias
Flap 5.............Vref + 40 Kias...136+40 = 176 Kias
Flap 10............Vref + 30 Kias...136+30 = 166 Kias
Flap 15............Vref + 20 Kias. 136+20 = 156 Kias
Flap 20............Vref + 10 Kias...136+10 = 146 Kias
Flap 30/full...Vref + 0 Kias....136+0 = 136 Kias

That is the ICAO Cat C Vat speed - range of final approach speeds for Cat C is 115-160kt ....

I dunno whether everyone's FCTM(FLT CREW TRAINING MANUAL) is the same....coz our says the "airplane can either be CAT C or D based on THE MAXIMUM LANDING WEIGHT'' and by this our MAX LDG WT 66360KGS which gives us CAT D all the time.