Step climb question

[bpcw0001]

I have been watching Victory AJs video on the step climb topic.

One point I‘ve been asking myself if you put the final flight level into the FMS and work with hold-down constraints, won‘t the box give you an „unable crz alt“ or some similar message?
It appears that the FMS does not check the max possible FL for the given weight?

 

 

[Pils]

On 9/1/2023 at 12:43 PM, bpcw0001 said:

One point I‘ve been asking myself if you put the final flight level into the FMS and work with hold-down constraints, won‘t the box give you an „unable crz alt“ or some similar message?

Why would it? You're still reaching the "cruise" level eventually... Assuming you're not trying to climb too high.

On 9/1/2023 at 12:43 PM, bpcw0001 said:

It appears that the FMS does not check the max possible FL for the given weight?

What makes you say that?

[bpcw0001]

11 hours ago, Pils said:

Why would it? You're still reaching the "cruise" level eventually... Assuming you're not trying to climb too high.

What makes you say that?

The procedure starts with putting the final flight level (let’s say FL410) into the FMS. With fuel quantity and loadout set for a long flight, I would have expected the FMS to initially complain at that stage during preparation where it does not have the hold-down constraints yet, telling me that FL410 doesn‘t work. Any warning would then go away only after the initial climb constraint to a lower flight level is established in the FMS.

Maybe I got it wrong?

 

[Pils]

12 hours ago, bpcw0001 said:

The procedure starts with putting the final flight level (let’s say FL410) into the FMS. With fuel quantity and loadout set for a long flight, I would have expected the FMS to initially complain at that stage during preparation where it does not have the hold-down constraints yet, telling me that FL410 doesn‘t work. Any warning would then go away only after the initial climb constraint to a lower flight level is established in the FMS.

Maybe I got it wrong?

I still think in this case you'd be reaching the selected CRZ FL eventually, and before Top of Descent, hence no message. What does LEGS and/or FPLN PROGRESS say for predicted altitudes at this stage of entry?

[bpcw0001]

On 9/3/2023 at 8:40 PM, Pils said:

I still think in this case you'd be reaching the selected CRZ FL eventually, and before Top of Descent, hence no message. What does LEGS and/or FPLN PROGRESS say for predicted altitudes at this stage of entry?

Ok, I played around with this a bit.

The box indeed calculates a veeeeery long and shallow climb up to FL410 to eventually reach that level as soon as it is attainable based on the predicted GW with the expected fuel burn-off. In my extreme test case, FL410 was basically reached shortly before TOD on a transatlantic route.

The FMS does complain if a too high altitude is put in too early, which is what I had expected:

 

I got how this works now. Thanks!

Edited September 7, 2023 by bpcw0001