CRJ - Actual landing distances - Non-normals

[dcoded]

I have been flying CRJ for quite some years, but it is only until a recent encounter in the sim with a new TRI the following question and confusion has popped up.

Let's say you are dealing with a system malfunction which will decrease the stopping capability of the aircraft.
In this example, let's look at HYD 2 LO PRES.

The actual landing distance now needs to be INSCREASED by a factor of 1.75 (with one thrust reverser operative).
Here the confusion starts:
In the note shown in the QRH, they don't refer to which section in the QRH to find the actual landing distance, nor does it refer to which specific table to use (Flaps 45, or Flap 20).
From experience PERF-04 covers Actual landing distnaces (ALD) for DRY, where as PERF-06 covers WET and CONTAMINATED.

In other Abnormals the QRH usually refers to ALD for FLAP 45 located in PERF-04, or PERF-06, but not in this case.

Lets now consider two different scenarios, one where the runway is DRY, and one where the runway is CONTAMINATED with Compacted Snow.

DRY:

PERF 04-5

31.000 kg gives around 948m (At 0 preassure alt)

In the notes below the table we find:
Vref - Speed at 50 ft screen height, FLAPS 45
----------------------------------------------------------------------------------------

CONTAMINATED:

PERF 06-25

31.000 kg gives 1362 m (0 pressure alt)

In the notes below we find

Distance: + 16 meters / kt above VREF FLAP 45

+ 116 meters when one thrust reverser inoperative

Now, the confusion is that the TRI is claiming that since we land at FLAP 20 with the above mentioned hydraulic malfunction, we need to add the 16 meters (Becasue the landing speed is Vref flap 45 + 12 knots), So according to him, we need to take 16meters X 12 knots = 192m, and add that to 1362 m = 1554m, and then add the factor of 1.75 according to the QRH.

Here is where our views are different.
I am arguing that we DON'T need to add these 192meters, Since the QRH is already giving us a Factor of 1.75 (With one Thrust reverser Operative).
By his logic, I asked why we shouldn't also apply the +116 meters for the One Thrust Reverser INOP according to the note in the ALD.
For that he could not give me an answer.

Is there any CRJ Guru in here who can shed some light onto this matter?
Also, if you could provide any reference to support your claim.

Thank you!

[Mad (Flt) Scientist]

OK, you must be talking CRJ900 (or CRJ705) since that 1.75 factor doesn't apply to the 200 or the 700 for that failure.

As a rule, the landing distance factors presented in the AFM (and QRH) consider all the related factors. So for a failure with reduced braking which also instructs a f20, Vref+x landing, the reduced braking, the changed flap and the changed speed are all included in the factor. there's no need to additionally account for the flap and the Vref adder.

It may be clearer to review what the AFM says, since it's not constrained by the need to be a succinct as the QRH.

[dcoded]

OK, you must be talking CRJ900 (or CRJ705) since that 1.75 factor doesn't apply to the 200 or the 700 for that failure.

As a rule, the landing distance factors presented in the AFM (and QRH) consider all the related factors. So for a failure with reduced braking which also instructs a f20, Vref+x landing, the reduced braking, the changed flap and the changed speed are all included in the factor. there's no need to additionally account for the flap and the Vref adder.

It may be clearer to review what the AFM says, since it's not constrained by the need to be a succinct as the QRH.

Thanks for the answer. Just as I thought. Now I will need to find something to back my claims with.
I will check if the AFM will say something.
And yes! It is regarding the CRJ900!

[Mad (Flt) Scientist]

If you look at the AFM presentation, you'll see that the ALD is defined as 0.6*LFL and the LFL chart (e.g. Fig 06-07-3) has no corrections for speed adders or anything similar.

Then the AFM tells you to apply the 1.75 to the ALD, which means the AFM ALD, obviously.

So if you calculate the failure distance using the AFM, you'll find (hopefully!!) that it agrees with the interpretation you have - no double accounting for the VREF adder is required.

The AFM is the definitive source for info - it's the actual certified, approved, manual. Things like the QRH and FCOM are derived from the AFM, and in case of contradiction the AFM will take precedence.

[safetypee]

MFS, as a side interest, #7 implies that the AFM and FCOM ‘actual distances’ differ.
Are the latter values (the FCOM ‘actual’), Operational Landing Distances (OLD or FOLD). If so then perhaps the potential ambiguity between the ‘actuals’ in AFM and FCOM should be clarified.

[dcoded]

If you look at the AFM presentation, you'll see that the ALD is defined as 0.6*LFL and the LFL chart (e.g. Fig 06-07-3) has no corrections for speed adders or anything similar.

Then the AFM tells you to apply the 1.75 to the ALD, which means the AFM ALD, obviously.

So if you calculate the failure distance using the AFM, you'll find (hopefully!!) that it agrees with the interpretation you have - no double accounting for the VREF adder is required.

The AFM is the definitive source for info - it's the actual certified, approved, manual. Things like the QRH and FCOM are derived from the AFM, and in case of contradiction the AFM will take precedence.

Thanks for the input.
However, I am having a hard time finding the references you point at. In our AFM, Chapter 6, Performance is around 30 pages in total.
Section 06A-06-01, covering Approach and Landing only contains one figure, regarding the Maximum Permissable Quick Turn-Around Landing Weight.

I am confused.

EDIT:
Can it be that the Performance section have been taken out of our AFM?
There are references to CAFM - Computerized AFM

[Mad (Flt) Scientist]

Can it be that the Performance section have been taken out of our AFM?
There are references to CAFM - Computerized AFM

Yes, if your airline bought the CAFM then the paper AFM is very much reduced in size.

You should be able to do the same calc in the CAFM for LFL etc as in the paper book.

[dcoded]

Yes, if your airline bought the CAFM then the paper AFM is very much reduced in size.

You should be able to do the same calc in the CAFM for LFL etc as in the paper book.
Thank you for clearing this up!!
Unfortunately, I don't have direct access to the CAFM. However, for my next session, I will bring this up as a topic.