Loss relief

You cannot make partial income tax loss relief claims in order to preserve the use of the PA. All that may be possible is to restrict the capital allowances claimed so as to give you the right amount of adjusted trading loss which when applied in full will still leave the taxpayer with sufficient income to cover the PA.
The new restriction however on the maximum amount of loss that may be set off against total income (see OT course notes) may have the effect of leaving sufficient income to cover the PA.

I assume by AA you mean the Annual Exempt Amount (AEA) for CGT purposes. Capital losses must be set off against all gains of the same tax year but when a capital loss is carried forward you only have to use sufficient to reduce the net gains of that year down to the level of the AEA.

PA and AEA may be used in the tax computations but the full title should be used in any written question.