Hi Bob,

I noticed someone posted about the question of low level jet streams are hazardous because they cause wind sheer. Because the older books had one answer and the current book has a different answer and the online exam had one of the 2, it has left me confused with is the hazard strong vertical or horizontal wind sheer at the surface and why so?

I am also having trouble comprehending the fuel and alternate aerodrome requirements as written in the book and AIP. The following is my understanding:

1. If the weather is forecasted to be good (above the minima listed in AIP) and you arrive within this period, no extra fuel or alternate AD is required.
2. If you are travelling to an aerodrome beyond 50nm, only then do you need extra fuel or an alternate AD if your arrival is within 30mins of deteriorating conditions (only those listed in AIP)
3. If weather is currently good and due to go bad from 0300 to 0600and your ETA is 0500 for example, you must carry enough fuel to assume the deterioration will start at 0230 and last until 0630. Vise versa for bad conditions changing to good, so assume it will stay bad until 0330 and only be good until 0530?
4. If TS are forecasted, you must plan and have enough fuel for an alternate AD
5. If an INTER is listed within the arrival time, you must take an extra 30mins of holding fuel and again assume 30mins buffer both sides
6. Same as number 5 but for a TEMPO, carry 60mins extra

In addition, do all of these apply only if the aerodrome is beyond 50nm? If not, which ones does it apply to (if my understanding is correct)
Also if there is an INTER or TEMPO in a TAF, do you need to carry the 30 or 60 mins holding fuel PLUS another 30mins for the buffer on either side?

I hope you can please clarify this for me so I understand it fully before my exam.

Thank you

When two adjacent air streams have significant differences in either speed or direction, a turbulent zone is created at the common boundary where the two air streams rub against each other. According to the current Manual of Meteorology, if the aircraft encounters that boundary during climb or descent, it is called vertical wind shear. If the aircraft encounters the boundary during level fight, it is called horizontal wind shear.

2. The 50nm limit applies only to VFR flights, there is no such limit for IFR. That's a strange one. If you are going beyond the vicinity of the airport (10nm), you MUST get a forecast. But, if you are VFR and going less than 50nm, you don't have to take any notice of it!!

3. Thunderstorms will always impose an OPR but it does not necessarily mean you need an alternate. See AIP ENR 1.1 para 11.7.2.5 and then AIP ENR 1.1 para 11.7.2.8. When the thunderstorms are prefixed INTER or TEMPO you can carry an alternate OR hold for 30 or 60 minutes respectively. That does not mean that you must carry the holding PLUS the alternate.

AIP ENR 1.1 para 11.7.2.1 says that for a VFR flight remaining within 50nm no OPRs apply.

Thank you Bob for that detailed response.

So that leads me to question 5 in the textbook on page 159 when the aircraft arrives at 0040.

So conditions are going from bad to good so assume it won't get better until 0130 (FM)
But do we assume the INTER starts at 0030 through to 0830?
Does that mean we should focus on the information on the INTER because the buffer falls closer to the arrival time?

Hence D

Thanks again

I can't find that question. Are you referring to the IREX book?

No it is in the Met book.
The question is in the practice questions for the area forecasts/TAF section.