Greg Boeser
1st Sergeant
Are you calling the author a liar?!!!!
True Air Speed Vs Indicated Air Speed
- Thread starter Laurelix
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MIflyer
1st Lieutenant
Well, one simple explanation is that the WX forecast had been for a substantial headwind but it turned out to be a significant tailwind.
Significant is not the word. The whole point of the problem with jetstream upper winds at that time is that they were not understood or forecast.
It would be good if you showed your detailed working for this particular mission.
BTW, I have a solution but, I am not too happy with it.
Eng
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A few points :
It would be very informative to know the home base and location of target on the mentioned raid on Norway. Common cartography representation of Europe distorts distances. From the location of most US bases in UK ( south east England) in WW2 to fjords north of Oslo is a LONG way.
The LW attacks on London on Sept 15 1940 were severely affected by headwinds. The attacking force was a mixed bag of old and new bombers of three types with many variants, escorts of Bf110s of various types and Bf109s of various types including Jabo variants. Even on the short range involved, it is around 100 miles from the form up area to London it was impossible to synchronise the attack and keep to a schedule. The Bf 110s ordered to fly with the bombers had to lower flaps at times to keep formation and the Bf 109s were running out of fuel long before they reached London.
Weather systems over Europe may involve jet streams but they are what they are, a mix of warm moist weather from across the Atlantic coupled with cold systems from the Arctic, warm or cold systems from continental Europe including Russia (depends on the time of year) and at times others from Africa which are generally warm. Below is an article about next weeks predicted storm named "Babet" it contains an animated progression of the weather. Note that the predicted winds in this storm from late October 2023 are from Calais to London, precisely the opposite of those on Sept 15 1940. As with most Brits, I take such things with a pinch of salt, it may happen, it could happen but they may have got it wrong and something else happens.
www.dailymail.co.uk
It would be very informative to know the home base and location of target on the mentioned raid on Norway. Common cartography representation of Europe distorts distances. From the location of most US bases in UK ( south east England) in WW2 to fjords north of Oslo is a LONG way.
The LW attacks on London on Sept 15 1940 were severely affected by headwinds. The attacking force was a mixed bag of old and new bombers of three types with many variants, escorts of Bf110s of various types and Bf109s of various types including Jabo variants. Even on the short range involved, it is around 100 miles from the form up area to London it was impossible to synchronise the attack and keep to a schedule. The Bf 110s ordered to fly with the bombers had to lower flaps at times to keep formation and the Bf 109s were running out of fuel long before they reached London.
Weather systems over Europe may involve jet streams but they are what they are, a mix of warm moist weather from across the Atlantic coupled with cold systems from the Arctic, warm or cold systems from continental Europe including Russia (depends on the time of year) and at times others from Africa which are generally warm. Below is an article about next weeks predicted storm named "Babet" it contains an animated progression of the weather. Note that the predicted winds in this storm from late October 2023 are from Calais to London, precisely the opposite of those on Sept 15 1940. As with most Brits, I take such things with a pinch of salt, it may happen, it could happen but they may have got it wrong and something else happens.
Video: Map shows path of ferocious Storm Babet when it hits Britain | Daily Mail Online
Storm Babet will sweep into Britain from tomorrow night, bringing up to eight inches of rain and ferocious 60mph winds amid warnings that buildings could collapse.
MIflyer
1st Lieutenant
Okay, I found the book, sneakily hiding on a bookshelf. it is "A Wing and a Prayer" by Harry H. Crosby. Great Book!
The Mission was Thorpe Abbots to Great Yarmouth and out over the North Sea to the target: Trondheim. Initial heading after the coast was 068. Total round trip was 1900 miles. They hit the clouds and ended up going to 18,000 ft before they broke out, 6,000 ft higher than originally planned. They found the target, hit it, and one B-17 was damaged by flak. They had been told that they would have a head wind but instead had a terrific tail wind. So the Nav recommended they head SW until they hit the Shetland Islands, the go down to 5000 ft, under the clouds until they hit Scotland. The command pilot agreed.
48 miles West of Trondheim they were intercepted by two JU88 and shot both of them down. The Luftwaffe had a lot of trouble finding them because the Nav did not know where he was most of the time and thus did not have the radio operator send out position reports. Enroute they flew over the only site on the West coast of Norway that had flak. They turned to 228 deg magnetic and then turned to 200 degrees. They went down to 3000 ft to get under the clouds. Once they found Scotland no navigator was needed
Note that the Nav did this without even going to the mission briefing and only knew where they were going when he opened the maps they gave him in the airplane. He had no breakfast and literally had to do things on the fly in real time. He figured he had done everything wrong, wrong course, wrong altitude, but they hit the target at a time so that no Norweigans were hurt and twice as many Germans killed, and had one airplane damaged with two crew not seriously hurt, with two Ju88 shot down, with no chutes seen.
The Luftwaffe musta crapped their pants.
The Mission was Thorpe Abbots to Great Yarmouth and out over the North Sea to the target: Trondheim. Initial heading after the coast was 068. Total round trip was 1900 miles. They hit the clouds and ended up going to 18,000 ft before they broke out, 6,000 ft higher than originally planned. They found the target, hit it, and one B-17 was damaged by flak. They had been told that they would have a head wind but instead had a terrific tail wind. So the Nav recommended they head SW until they hit the Shetland Islands, the go down to 5000 ft, under the clouds until they hit Scotland. The command pilot agreed.
48 miles West of Trondheim they were intercepted by two JU88 and shot both of them down. The Luftwaffe had a lot of trouble finding them because the Nav did not know where he was most of the time and thus did not have the radio operator send out position reports. Enroute they flew over the only site on the West coast of Norway that had flak. They turned to 228 deg magnetic and then turned to 200 degrees. They went down to 3000 ft to get under the clouds. Once they found Scotland no navigator was needed
Note that the Nav did this without even going to the mission briefing and only knew where they were going when he opened the maps they gave him in the airplane. He had no breakfast and literally had to do things on the fly in real time. He figured he had done everything wrong, wrong course, wrong altitude, but they hit the target at a time so that no Norweigans were hurt and twice as many Germans killed, and had one airplane damaged with two crew not seriously hurt, with two Ju88 shot down, with no chutes seen.
The Luftwaffe musta crapped their pants.
drgondog
Major
Blitz week 24 July 1943.
100th BG and 95th BG tasked for Trondheim, 1st BW went to Heroya, the rest of 4W went to Bergen.
Harry Crosby was 100th BG Nav
The 8th Mission Summary for VIIIBC FO 75 states that the second 4BW tasked for Bergen encuntered 10/10 over the target and bought their bombs home. Noted a 1900mi round trip - at that time the longest bombing mission of WWII to date
100th BG and 95th BG tasked for Trondheim, 1st BW went to Heroya, the rest of 4W went to Bergen.
Harry Crosby was 100th BG Nav
The 8th Mission Summary for VIIIBC FO 75 states that the second 4BW tasked for Bergen encuntered 10/10 over the target and bought their bombs home. Noted a 1900mi round trip - at that time the longest bombing mission of WWII to date
Yup, everywhere in Norway is further away from UK than even people in UK think it is.
So, there is quite a bit to sort this out. Several factors are at play; IAS/TAS, MPH/KNOTS, Statute miles/Nautical miles, Jetstreams, and what was actually done by the Mission.
The details of the Mission have changed a lot. However, I believe the basics are, The B17G raid went from Thorpe Abbotts, with a fairly direct route to bomb at Trondheim, was on target 2 hours earlier than planned-for, with a headwind, but got a strong tailwind instead and cruised there at 18,000' instead of 10,000' due to cloud. Off target they went West a bit, then south towards Scotland, having descended to 3000' due to cloud (and maybe to get out of the headwind). Got home to Thorpe Abbotts after 1,900 miles.
The total miles could be Statute Miles. The standard B17G tables don't show a 1900 nm mission profile but, 1900statute miles is 1651nm and there are mission profiles with radius/range to do that. (edit, see below). The direct distance to Trondheim in nm is about 740nm and I am guessing 750nm to target and 901nm home. The speeds they flew are not more closely quoted but the performance tables show an option (basic range II) that gives a TAS 156 knots average at 10,000', and that equates to an IAS of 150 mph!
So, to illustrate a possible way this worked, here is a solution.
The plan included a "strong" headwind component at 10,000'. So, if we take the 150mph IAS that is 130kt and corrects to 155kt TAS. Use a 25kt Headwind, leaves 130kt G/S for 750nm, so a planned elapsed time 5hrs 45min. However, they actually flew at 18,000' and the 150mph IAS would correct to 175kt TAS. The wind was different and gave a 25kt Tailwind so that gives 200kt G/S for 750nm, with elapsed time 3hours 45min.
So that illustrates the possibility to save 2 hours, against a plan that changed to a higher TAS (+20knots) and a total change of wind from -25kt to +25kt (+50knots) giving a speed 70knots faster than plan, and 2 hours less.
The actual wind change would have been different (probably more wind for shorter period) but, these figures can work.
Overall, forecasting these winds was very basic back then. Also note, slow aircraft are greatly affected by headwinds that are a large percentage of their speed.
Eng
Edit. 8th Air Force Historical Society shows total range of mission as several values, including, quote 1900 miles and 3040 kilometers. That comes out as 1650 or so Nautical Miles.
Also lists attack as 45 aircraft with 41 bombed. I aircraft crashlanded at Fraserborough (Scotland) with 3 wounded.
The details of the Mission have changed a lot. However, I believe the basics are, The B17G raid went from Thorpe Abbotts, with a fairly direct route to bomb at Trondheim, was on target 2 hours earlier than planned-for, with a headwind, but got a strong tailwind instead and cruised there at 18,000' instead of 10,000' due to cloud. Off target they went West a bit, then south towards Scotland, having descended to 3000' due to cloud (and maybe to get out of the headwind). Got home to Thorpe Abbotts after 1,900 miles.
The total miles could be Statute Miles. The standard B17G tables don't show a 1900 nm mission profile but, 1900statute miles is 1651nm and there are mission profiles with radius/range to do that. (edit, see below). The direct distance to Trondheim in nm is about 740nm and I am guessing 750nm to target and 901nm home. The speeds they flew are not more closely quoted but the performance tables show an option (basic range II) that gives a TAS 156 knots average at 10,000', and that equates to an IAS of 150 mph!
So, to illustrate a possible way this worked, here is a solution.
The plan included a "strong" headwind component at 10,000'. So, if we take the 150mph IAS that is 130kt and corrects to 155kt TAS. Use a 25kt Headwind, leaves 130kt G/S for 750nm, so a planned elapsed time 5hrs 45min. However, they actually flew at 18,000' and the 150mph IAS would correct to 175kt TAS. The wind was different and gave a 25kt Tailwind so that gives 200kt G/S for 750nm, with elapsed time 3hours 45min.
So that illustrates the possibility to save 2 hours, against a plan that changed to a higher TAS (+20knots) and a total change of wind from -25kt to +25kt (+50knots) giving a speed 70knots faster than plan, and 2 hours less.
The actual wind change would have been different (probably more wind for shorter period) but, these figures can work.
Overall, forecasting these winds was very basic back then. Also note, slow aircraft are greatly affected by headwinds that are a large percentage of their speed.
Eng
Edit. 8th Air Force Historical Society shows total range of mission as several values, including, quote 1900 miles and 3040 kilometers. That comes out as 1650 or so Nautical Miles.
Also lists attack as 45 aircraft with 41 bombed. I aircraft crashlanded at Fraserborough (Scotland) with 3 wounded.
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I presume mission planning involved returning to home base. However there was always a contingency. There were a large number of Coastal Command airfields in Scotland, the Scottish Islands and Northern Ireland capable of taking a B-17, some operated B-17s and Liberators. It is 445 miles from Gt Yarmouth to Wick which is at the northernmost point on the Scottish mainland and had a 6,000ft runway.
Hi,
Yes, there were quite a few cut-short options with a track back south, although the long sea track was the bogey-man (if you ditched / bailed-out).
I do not have the further details of this raid, but I believe these are the basics of the profile, as given.
The actual range, speeds and loads of the B17G are quite complicated, I am certain this flight detail is more complicated, but B17 Ops is not my speciality. However, the general format
of this raid can be understood, and the effect of the winds appreciated. For these slow aircraft, the effect of the winds is notable and the consequences of an inaccurate
headwind on a long range flight are great.
I tried to simple research the forecasting of upper winds in July 1943, but information is vague. I suspect that there was little valuable forecasting or even reporting of winds 25,000' and above. Possibly, some information would be forecast upto 25,000' for Central/West Europe, based on the lower level synoptic prognosis, but this would be limited over towards Norway, and would not really include Jetstream plots, AFAIK.
In this case, the -25/+25knots wind component stacks-up with a +20knots TAS change from the plan to give an almost +50% increase in groundspeed to a long range target, so although +/-25 knots doesn't seem much, it has a big effect on low speeds. In fact, if the winds had varied in the opposite sense on this mission to give -70knots, the mission would be out of fuel at the target after 10 hours or so flying.
Eng
WRT wind, I suspect the USAAF would have had RAF Meteorological officers attached to their units. This was the case on RCAF 6-Group stations. Originally civilians, they were moved over to the RAF at some point during the war. The vagaries of weather forecasting in the UK would have been a very steep learning curve.
On dad's operation to Bergen Norway, 4-October-1944, they had GEE coverage all the way to Bergen and back. I have the Navigator's form for this and they were early on target by one minute. I find the 2 hour early on target for the raid described above astounding! Dad's navigator had them 6 minutes early on target to Bochum, 9-October-1944 and he was reprimanded for this transgression and told not to let it happen again.
Here is the State of the art of weather forecasting for an operation of my dad's, late war. Lovely penmanship!
On dad's operation to Bergen Norway, 4-October-1944, they had GEE coverage all the way to Bergen and back. I have the Navigator's form for this and they were early on target by one minute. I find the 2 hour early on target for the raid described above astounding! Dad's navigator had them 6 minutes early on target to Bochum, 9-October-1944 and he was reprimanded for this transgression and told not to let it happen again.
Here is the State of the art of weather forecasting for an operation of my dad's, late war. Lovely penmanship!
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Thanks JD,
Yes, there is no doubt there was a lot of effort on Met reports, but I believe this was mostly after missions reported back, so the forecasts were rudimentary and things like Jetstreams that can move in quickly caught missions out. There was a lot of effort into Met flights over the Atlantic approaches, lost quite a few aircraft into the great Ogg. I have read of windfinding flights to support raids with more up to date info. Later Navaids like GEE were great but the Day mission to Trondheim seems to have been mostly DR Nav, visual fixing and possibly sunshot sextant.
Yes, there is no doubt there was a lot of effort on Met reports, but I believe this was mostly after missions reported back, so the forecasts were rudimentary and things like Jetstreams that can move in quickly caught missions out. There was a lot of effort into Met flights over the Atlantic approaches, lost quite a few aircraft into the great Ogg. I have read of windfinding flights to support raids with more up to date info. Later Navaids like GEE were great but the Day mission to Trondheim seems to have been mostly DR Nav, visual fixing and possibly sunshot sextant.
drgondog
Major
I am curious why he was reprimanded for being 'six minutes early'? What was he supposed to do - accurately predict the winds aloft and order changes to actual ground speed? Was the instrumentation associated with GEE accurate enough that the navigator should have known?
What were consequences to missing waypoint/time by six minutes? Potential Mid Air Collision with other RAF crews experiencing similar navigation issues?
For 8th AF/15th AF R/V and time precision issues were greatest when the R/V was for fighter escort... and there were real consequences for the bombers if the LW was 'on time at the right place'. Being Off Course for fighter escort R/V was the Greater problem on April 29, May 12, June 20, July 7, September 27, 1944, etc.
Well, Bomber Command stressed timing to keep the stream together. The ORBs reveal other crews on the Squadron bombed on time, so this was not acceptable. I quizzed Marvin Seale about this and he said:
"Prior to take off the navigation leader "Pop" Thompson gave me a pep talk: ….anymore goof ups like that [in reference to early timing on previous raid to Bochum] and I would be in serious jeopardy of some sort of what sort I don't know. He was a high school teacher from a little school in Alberta and was the navigator for "Strip Tees" (F/O J.F. Tees) and had been removed from that crew to become navigation leader."
Dad recalled: "We also had, for the first time, jamming [of] the Gee and Marv Seale was unable to get any really good fixes until just as we were approaching the "Gap" between Dusseldorf and Cologne. We were obviously attacking the target from the southern part, going through the "Gap" and then turning north for the attack to Bochum. Anyway, just as we were getting to the "Gap", Marv said, "My God. I've got a fix finally and we are very early. We are six and a half minutes early" or eight minutes early I think by that time. "You will have to do 2 360o turns to waste the time". Now this happened just as we were coming into the "Gap". Now if I had made those two 360o turns, I would have been in deep, deep trouble. So I said "Marv, I can't do it! I'm not doing it!" And so I throttled back and put the flaps down and we hovered and went as slowly as we could. But of course we only lost about a minute and a half by this little effort on my part. So we bombed six and a half minutes early."
The jeopardy of doing a 360 orbit in the middle of the Bomber stream was of the greatly increased risk of collision when perpendicular to the aircraft flying in the Stream. In his book, Murray Peden talked about the danger of doing an orbit, as he actually did one. Very frightening!
WRT weather, the forecast for 5/6-March-1945 above, was not accurate. The weather was much worse than forecast. Seven aircraft from RCAF squadrons crashed shortly after takeoff, killing 40 aircrew. Icing was severe. Weather was similarly poor on return over France and England with 4 more aircraft crashing killing another 24 airmen. dad was on this op and I have Seale's navigator log and chart.
Edit: I should add that dad disobeyed the Flight Plan for the return trip over France which called for a height of 3,500'. The Nav log records that dad flew at 15,000', well above cloud to avoid severe icing.
Jim
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drgondog
Major
thanks - made sense, as well as the reliance on GEE.
Thanks for the extra info about the March 1945 raid Met. I see at the top line in the matrix (Synoptic situation), it actually say's "SECRET, please complete at 1930hrs and return". I can understand the raid-related info being Secret and I guess the document was tracked for return after briefing/planning.
Noted that the limited icing warning possibly accounted for the deaths of 64 crew at this late stage of the European War.
As far as timing of TOT. My understanding of later war RAF night bombing tactics is that the aim was to compress the bomber stream to minimise exposure to defences, achieve concentration of force on target and make target marking an achievable technique. However, there were consequences of excessive "crowding" if everyone had the same TOT and so, it became important to make an accurate TOT on a plan, that was as compressed as thought to be effective. Pressuring crews to achieve TOT was possibly fair.
Eng
MIflyer
1st Lieutenant
Later, when they had P-51's, they would send out Weather Scouts, a flight of four Mustangs, to report on the WX in the target area and presumably unforecast winds. Of course, the WX Scouts were not adverse to bagging a few Luftwaffe aircraft that they ran across during the course of their primary mission. I think I have an article on that somewhere.
I wonder what they did for radio communications for the WX Scout missions. The SCR-522 radios the Mustangs in the ETO were equipped with normally could not reach GB from Germany, but they did stage radio relay aircraft between GB and the mainland, usually P-47's, I think.
I wonder what they did for radio communications for the WX Scout missions. The SCR-522 radios the Mustangs in the ETO were equipped with normally could not reach GB from Germany, but they did stage radio relay aircraft between GB and the mainland, usually P-47's, I think.
