Weather Minimums for Operations

[gecko]

I was recently reading about RAF Rhubarb operations, and saw that the minimum cloud ceiling was 2,000ft, later reduced to 1,500ft. This surprised me as I thought they would go in much worse weather. There's a war on after all. So now I'm curious what the weather minimums were for different operations. Cloud height, daylight limits, wind speed/crosswind, weather at home base vs weather at the target, etc. I know this is a fairly broad question and will probably vary by air force, aircraft type, type of mission, etc. I am interested in all of it and any specific information or resources that might be available.

Thanks,

Dan

 

[yulzari]

These are ceilings above sea level. Across the ground they can leave much less space than the bare figures. Across northern France 1,500 feet can actually leave just single figures of hundreds of feet of clearance and the given figures are not guaranteed to be correct across the whole area nor the whole period of an operation. Not to mention that the purpose was to bring the Luftwaffe to battle. Which is a touch tricky in a cloud.

 

[gecko]

These are ceilings above sea level. Across the ground they can leave much less space than the bare figures. Across northern France 1,500 feet can actually leave just single figures of hundreds of feet of clearance and the given figures are not guaranteed to be correct across the whole area nor the whole period of an operation. Not to mention that the purpose was to bring the Luftwaffe to battle. Which is a touch tricky in a cloud.

Thanks for your response, that's interesting. I wasn't sure whether they would have used MSL or AGL for cloud heights. Where is your information from? I would love to see what else can be gleaned from that source. Per the original post, I'm interested in anything having to do with weather criteria for operations in WWII.

Thanks

 

[BiffF15]

Thanks for your response, that's interesting. I wasn't sure whether they would have used MSL or AGL for cloud heights. Where is your information from? I would love to see what else can be gleaned from that source. Per the original post, I'm interested in anything having to do with weather criteria for operations in WWII.

Thanks

I don't know for certain but using anything other than AGL would mean your doing math in the cockpit to figure out where you should or if you will break out of the weather.

 

[gecko]

Using MSL or AGL is going to result in some mental math, just depends on the situation. In modern aviation weather forecasts MSL is used for wide areas since our altimeters are set to MSL, and AGL cloud heights are very dependent on location. AGL is used for reporting cloud heights in the immediate vicinity of an airport, as AGL cloud height is the determining factor for what kinds of operations can be conducted there, and AGL can be given based on the known elevation of the airport. For flights conducted visually, such as a rhubarb would have been, the cloud height along the route is estimated as closely as possible based on the reported or forecast MSL height of the clouds and the terrain elevations of the route, and that is used to make a go or no-go decision.

That last part is what I'm after. What were the criteria used for determining whether to send aircraft on a mission? At what point is someone saying, "Ok, the weather is too bad to launch this Circus operation because clouds are too dense or too low, but it looks like we can still send out some rhubarbs." Or, "the winds are too high for safe landings.and takeoffs, we have to scrub today's mission." That kind of thing. I'm assuming someone somewhere is making those kinds of decisions based on some kind of established criteria for the kind of operation to be flown. I know different air forces probably had different standards and applied different criteria for different kinds of operations. I'm hoping for any sources for any nation that describe the criteria they used.

 

[cvairwerks]

Operational weather limits are based on what aircraft are being flown and training standards. Different a/c had different limits based on performance limitations within the flight manuals. Prior to the development of current landing aids, if you couldn't see a certain distance, you didn't fly. These days, with the capabilities that have been developed, we can fly in near zero visibility and do so safely.

For any particular a/c, look at the POH and dive into the performance standards.

Forgot to add, winds aloft, direction, temp, humidity and barometric pressure all come into play. Having strong enough headwinds enroute or coming back might mean that the bomb load is too small go deal with when you load enough fuel to go to the target and get back to home, or an alternate.

 

[gecko]

Operational weather limits are based on what aircraft are being flown and training standards. Different a/c had different limits based on performance limitations within the flight manuals. Prior to the development of current landing aids, if you couldn't see a certain distance, you didn't fly. These days, with the capabilities that have been developed, we can fly in near zero visibility and do so safely.

For any particular a/c, look at the POH and dive into the performance standards.

Forgot to add, winds aloft, direction, temp, humidity and barometric pressure all come into play. Having strong enough headwinds enroute or coming back might mean that the bomb load is too small go deal with when you load enough fuel to go to the target and get back to home, or an alternate.

As a pilot and warbird enthusiast, I have read quite a few POHs, Pilots Notes, etc, and they don't give weather criteria, with the exception of maximum demonstrated crosswind, which is not considered a limitation. They give expected performance in different conditions. While interesting, it doesn't tell me anything about what minimum ceiling (visibility, winds, etc) the RAF or USAAF or Luftwaffe or anyone else would scrub a mission if not met.

 

[ThomasP]

I do not know if this is what you are looking for but:

Around 1930 the RN/FAA considered the limit for carrier flight operations to be Beaufort 6 (winds of 22- 27 knots, waves of 9-13 ft), a decision based on the light weight biplane aircraft of the time being blown around. Around 1935 the RN/FAA began to train for night operations, with the intent of being able to attack shore targets (and ships if they were locatable) day or night in any weather in which the carrier aircraft would operate.

By the beginning of WWII, the RN/FAA had settled on Beaufort 7 - day or night - as the limit on operations from carriers decks. The Beaufort scale does not cover visibility(?), but there are reports describing take-off operations with very low ceilings and limited visibility - ie not being able to see the bow from the deck spot (ie 400-500 ft) due to fog. There are also reports of recovery operations in very limited visibility, and of very low cloud ceilings. (There is one report from the North Atlantic with an ASV equipped Swordfish approaching the carrier at an altitude of 50-100 ft ASL with the aircraft pulling up to 175-200 ft ASL at ~1000 ft/10 sec from the stern of the carrier in order to complete recovery. Ceiling was estimated as ~200 ft and visibility was ~1500 ft eeek!).

The USN on the other hand, would normally not operate aircraft above Beaufort 5 due to landing ops being too problematic at higher sea states and wind speeds.

I did run across a dispatch (on the internet) a few years ago that described what the US 8th AF considered the limits for normal heavy bomber operations, but I did not download/copy the information at the time, and subsequently lost track of it.

 

[cvairwerks]

As a pilot and warbird enthusiast, I have read quite a few POHs, Pilots Notes, etc, and they don't give weather criteria, with the exception of maximum demonstrated crosswind, which is not considered a limitation. They give expected performance in different conditions. While interesting, it doesn't tell me anything about what minimum ceiling (visibility, winds, etc) the RAF or USAAF or Luftwaffe or anyone else would scrub a mission if not met.

Guess you never had to work out the performance data for a flight then......I've always had to for my flying...fuel burn, range, take off and climb schedule. I've had instances where data is completely off the charts and had to cancel a planed flight.

 

[gecko]

Guess you never had to work out the performance data for a flight then......I've always had to for my flying...fuel burn, range, take off and climb schedule. I've had instances where data is completely off the charts and had to cancel a planed flight.

Strange to assume that because performance charts don't have the data I am interested in finding right now that I don't use them when I fly. Yes, you may use them to determine whether or not to launch, and they do take into account certain atmospheric conditions, but when somebody asks about weather minimums, they aren't talking about performance charts.

I do not know if this is what you are looking for but:

Around 1930 the RN/FAA considered the limit for carrier flight operations to be Beaufort 6 (winds of 22- 27 knots, waves of 9-13 ft), a decision based on the light weight biplane aircraft of the time being blown around. Around 1935 the RN/FAA began to train for night operations, with the intent of being able to attack shore targets (and ships if they were locatable) day or night in any weather in which the carrier aircraft would operate.

By the beginning of WWII, the RN/FAA had settled on Beaufort 7 - day or night - as the limit on operations from carriers decks. The Beaufort scale does not cover visibility(?), but there are reports describing take-off operations with very low ceilings and limited visibility - ie not being able to see the bow from the deck spot (ie 400-500 ft) due to fog. There are also reports of recovery operations in very limited visibility, and of very low cloud ceilings. (There is one report from the North Atlantic with an ASV equipped Swordfish approaching the carrier at an altitude of 50-100 ft ASL with the aircraft pulling up to 175-200 ft ASL at ~1000 ft/10 sec from the stern of the carrier in order to complete recovery. Ceiling was estimated as ~200 ft and visibility was ~1500 ft eeek!).

The USN on the other hand, would normally not operate aircraft above Beaufort 5 due to landing ops being too problematic at higher sea states and wind speeds.

I did run across a dispatch (on the internet) a few years ago that described what the US 8th AF considered the limits for normal heavy bomber operations, but I did not download/copy the information at the time, and subsequently lost track of it.

This is much more the kind of information I am looking for. Thanks! Convenient thing about carrier ops that you can make sure the wind is straight down the deck, but those waves won't make that easy. Would love to see that 8th AF source if it ever turns up.