Aircraft blueprint reading

[MiTasol]

Anybody have any suggestions on how to learn to read blueprints better. I am somewhat weak in that area and my job responsibilities are about to change. My employer has no problem with them but he does not have very much time to teach me what I should know. I was hoping for a website or a book or something I could study. I took some electrically related classes a while back but they just glossed over reading prints. Any ideas? Thanks

I may be wrong but I think this member is more after learning how to read electrical blueprints so he needs a site that covers all the regular electrical symbols rather than one on aviation blueprints. My knowledge on that is all pre digital and rusty so of no use to them.

 

[special ed]

Electrical circuit diagrams?

 

[MIflyer]

A word of caution: If you are wanting to learn to read aircraft drawings, they can get pretty complicated in a hurry.

I recall back at Tinker AFB someone had input a suggestion that we do something to extend the life of the F-111 cockpit air conditioning vents. I had noted some time before that we were using a lot of the things - and what wears out in a vent? I had found that it was impossible to climb into an F-111 without putting your hand on the vent; they had provided a place to put your foot but nowhere to grab with your hand.

So I got the General Dynamics drawings and had our shops build two examples, one made with 0.040 AL overall and one made with 0.050 AL overall, rather than the .020 and .032 AL material originally specified. The sheet metal shop guys said, "The drawing says there is a lip here." while pointing at a spot on the drawing. I replied, "No it does not! And GD and half a dozen small firms have built these without putting a lip there!" They insisted there was a lip and I did not object further, since for evaluating a stronger example it made no difference and they test examples would not have to be installed on an airplane. I looked at the results, decided to go with the 0.050 version and had a note added to the procurement requirements. A comparatively simple part, and the ALC shop people could not properly interpret the drawing.

When the first procurement was made of the new version I specified that a first article example would be supplied so I could look at the new version. The procurement guys asked me why I wanted to do that since we had bought literally hundreds of those before. I told them it was a new version I had designed and I needed to see it.

The first article samples came and I noted with approval that they were stronger than the old ones. But wait a minute! I had both one of the old ones and the two experimental ones still in my desk drawer. Comparing them, I found the new manufacturer had made a serious mistake. There was a Right and a Left version of the vent, basically mirror images of each other, and the new manufacturer had made one that was "half and half," mixing parts from the two different versions to make a type that would not fit the airplanes. I rejected the samples.

So there you go. A simple enough part, but different supposedly qualified people could not agree on what the drawing said.

 

[MiTasol]

Electrical circuit diagrams?

with the related installation (routing) drawings is what I suspect.

 

[MiTasol]

I recall back at Tinker AFB someone had input a suggestion that we do something to extend the life of the F-111 cockpit air conditioning vents. I had noted some time before that we were using a lot of the things - and what wears out in a vent? I had found that it was impossible to climb into an F-111 without putting your hand on the vent; they had provided a place to put your foot but nowhere to grab with your hand.

So I got the General Dynamics drawings and had our shops build two examples, one made with 0.040 AL overall and one made with 0.050 AL overall, rather than the .020 and .032 AL material originally specified. The sheet metal shop guys said, "The drawing says there is a lip here." while pointing at a spot on the drawing. I replied, "No it does not! And GD and half a dozen small firms have built these without putting a lip there!" They insisted there was a lip and I did not object further, since for evaluating a stronger example it made no difference and they test examples would not have to be installed on an airplane. I looked at the results, decided to go with the 0.050 version and had a note added to the procurement requirements. A comparatively simple part, and the ALC shop people could not properly interpret the drawing.

When the first procurement was made of the new version I specified that a first article example would be supplied so I could look at the new version. The procurement guys asked me why I wanted to do that since we had bought literally hundreds of those before. I told them it was a new version I had designed and I needed to see it.

The first article samples came and I noted with approval that they were stronger than the old ones. But wait a minute! I had both one of the old ones and the two experimental ones still in my desk drawer. Comparing them, I found the new manufacturer had made a serious mistake. There was a Right and a Left version of the vent, basically mirror images of each other, and the new manufacturer had made one that was "half and half," mixing parts from the two different versions to make a type that would not fit the airplanes. I rejected the samples.

So there you go. A simple enough part, but different supposedly qualified people could not agree on what the drawing said.

Yeah. We had a rush mod to do on an aircraft and the initial drawings arrived with a note Left hand drawn - right hand similar. Also supplied were some of the parts and a note that the balance of the parts will come next week. We got stuck in and did the left hand side as much as we could and then on Monday a bunch more parts arrived and we fitted them to the left also.

Next we asked when are the parts for the right hand side arriving only to be told that they were only to be installed on the right. We pointed out that NOWHERE on the drawing stated that. The answer was on the work order. Where on the work order we asked. The work order said install in accordance with drawing X. OOPS - they forgot to put it on the work order as well as the drawing.

Another drawing from the same draftsman could be read 5 different ways depending on which of the many reference points on the drawing. The manufacturer told us to check the aircraft that had been factory modified so we did (5 of 6 were factory done). We found four different installations including one of which we had not picked up on.

 

[MIflyer]

Back in the late 60's we lost a B-52 loaded with nuclear weapons in Greenland. It seems that a seat cushion got dropped under the seat where the hot bleed air of the "footwarmer" vent set it afire. Not only did the airplane crash, but we lost two of the crew. As a result the footwarmer vent was modified to put the holes along the back of the raised section where they were drilled, and a deflector was installed so that the hot air could not impact directly on any cushions but had to bounce off the deflector and make a 180 degree turn to get out from under the seat. Attachments were made to the drawings to reflect the change.

The engineer responsible for that and many other B-52 items always asked for first article samples from the manufacturer and when some came in for the foot warmer vent he found that the holes had been drilled along the front, not the back. He pointed out the problem and sent the parts back. I told him he should take a Sharpie marker and indicate where the holes should be. He scoffed at me, the dumb kid fresh out of college trying to tell an engineer with 20 years of experience in that stuff what to do, "Oh, come on! These people are not idiots.; they can read a drawing!"

The second try on the footwarmer vents came in and this time the holes were indeed drilled along the back - but rather than spacing the first one the given dimension from the edge and the rest at the specified dimensions from the first one - so that the holes would only proceed about halfway along the part - they had spaced the 2nd and subsequent holes equally, so they covered the whole length. That would not work, since the footwarmer slid underneath the aircraft toilet. This time the highly experienced engineer listened to the dumb kid and got out the Sharpie marker.

 

[MIflyer]

Next we asked when are the parts for the right hand side arriving only to be told that they were only to be installed on the right.

An engineer I worked with at Tinker AFB said that he knew guy who worked at Boeing Wichita on the production line and one day they arrived at work to find the previous shift had installed some items on the fuselage that would prevent them from installing the items they had the job to handle. So they removed the items that had been installed, which took a whole shift and they did not get to do their own work. When they came back the next day they found the previous shift had installed the other items again and they again spent their shift taking them off. This went on for a full week, as they tried to get someone in management to realize what was going on. Finally, the next week they were able to get the job done.

This is an unusually severe version of what so often happens when you are building a house and discover too late that you have scheduled the electricians and the plumbers for the same day.

 

[SaparotRob]

I think the 3 Stooges pulled it off.

 

[spanishbuddha]

Different companies have their own approaches. Boeing's was different from most others. I can recall an engineer in our office unfolding a drawing and saying, "Oh, God! It's from Boeing!" and then going to get a fresh cup of coffee. He knew he was going to be at that task for a while.

For sheet metal parts Boeing would put things like "BUP" on the drawing. I asked a highly experienced engineer what that meant. He replied, "It means Bend Up." That meant that flat drawing representing the layout of a sheet metal part indicated that part of the metal should be bent upwards along the bend line. He could handle understanding it with no problem, which meant that drawings needing engineering review prior to procurement actions got stacked up around his desk, since few others could make heads or tails of them. He also asked for First Article review of the parts that were to be delivered, because he had seen far too many cases where a part that "Joe's Screen Door Repair and Airplane Parts" should have been able to build per the drawing but would screw up in some way.

General Dynamics and Grumman used the same approach for their drawings. They standardized when they were both going to be building F-111's and Grumman kept the GD approach after the Navy part of the program was cancelled.

Hello.
I'm helping my stepson with his homework for his Blueprint Reading class. There's a question regarding the tolerances on the print.

The tolerances on the print reads:

"Decimal" "xxx +/- .010" "+/- xx +/- .020"

Never having taken any similar classes, I don't understand why there are multiple tolerances listed?

The actual question he has to answer is : "What is the significance of the tolerance xx +/- .020?"

Thanks! :

 

[MIflyer]

I could not even hazard a guess on that without seeing the actual drawing.

 

[ThomasP]

The number of "x" indicates the number of digits to the right of the decimal point.

If a dimension is written as 10.250 (ie 10.xxx) the tolerance would be +/-.010. If the dimension is written as 10.25 (ie 10.xx) the tolerance would be +/-.020.

 

[cvairwerks]

To build on Tom's reply, that tolerance note is a general guideline for the drawing, but is not absolute. There are times that the design may require a different tolerance at a specific location. In those cases, the specific numbers will be specified at the dimension location. For example, you might have a specific dimension that is 10.250" -.005"/+.007". In that case the requirement is that the dimension can be as much as .005" under the 10.250" and as much as .007" over.

 

[MiTasol]

And the November 1942 US standard for creating Engine blueprints, much of which is equally relevant to airframe and component blueprints. A loose leaf manual so designed to be revised.