Dumb Design Decisons

WTF?  Have you ever looked at something and said to yourself, "That is a really dumb idea."?

"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius -- and a lot of courage -- to move in the opposite direction."
--- Albert Einstein

"Everything should be made as simple as possible, not just simpler." --- Albert Einstein

I'm sure you've seen them: Someone has an idea about how something should be done and doesn't care how his design interacts (interferes) with any other part. I've seen a lot of dumb design decisions. Some of the design decisions were the result of 'just-being-lazy.'  Some I'll look at and think, "This must have been designed by a first year engineering student."  Others weren't thought out very well at all. 

Mechanics are the worst: I have lost count of the number of times I've opened a cowling and seen wired draped all over the place.  It's like Goober saying, "Well, this is the fastest way to do it.  Yea, who cares if the next guy can't change the oil filter?  I did this installation in 10 minutes.  Next."

Dumb Designs:  These poorly thought-out design decisions make the airplane more costly to produce and make maintenance more difficult.  Designs that make maintenance difficult could affect airworthiness:  some are so bad that some might mechanics will skip them.  Designs like these cost the owner much more than it should in the long run.  I've show cased the most aggravating ones.  Maybe, just maybe, some of these items will be considered if and when the next Tiger goes into production.

Here are some design decisions which need to be re-thought

AG5B:  The AG5B was designed by committee. Trust me, I've been in enough committees to recognize the results. 

• Engine gauges that you can't see because they are behind the throttles.  Plus, they are so low that to see them, you need to bend down to see the top of the gauge.

Later AG5Bs fixed this.

• Eyebrow light assemblies (just the light sockets) that cost $50-$70 each (in 1990 dollars)

• One-piece Carbon Fiber lower cowling:  in and of itself, is not such a bad idea.  But, riveting the 10.5 inch wide carb air box to the side so that removing and

installing the lower cowling becomes nearly impossible is just plain stupid. It's impossible to remove without scaring the engine mount.. . (I fixed this with a NACA inlet) 

• Using the same cowling latches used on the AA5x series and making the upper cowling so stiff it is difficult to open and close. 

Over time, the locking pins, which are a safety hazard to begin with, damage the lip on the lower cowling where they hit.

• The throttle quadrant intrudes into the cabin 4 inches more than on the AA5x, decreasing interior room and reducing knee room.   

I'm 6 feet tall and I get a terrible cramp in my right leg when flying an AG5B.

• The throttle quadrant is VERY expensive to make and VERY difficult to work on.  The throttle cable in an AA5B can be changed in 20 minutes.  

Figure several hours to change one in an AG5B.

• The committee decided the Tiger needed heated air to the back seat. Did anyone even consider that the average number of passengers is about 1.5; INCLUDING THE PILOT? 

Heated air is ducted down a new fiberglass (i.e., heavier) center console.  This plenum eats up 1 1/2 inches of footroom on each side.  Heated air is channeled through this plenum from a plemun behind the panel, into the console through 1 inch SCAT.  Again, that, in and of itself, is not a bad idea.  BUT, the flange on the plenum does not line up with the flange on the center console and impossible to get the 1 inch SCAT installed. Fit and finish suck on this design.

• It should have been fitted with a 180 hp IO360 and constant speed prop.

• Retractable should harnesses.  In and of itself it's not a bad idea.  But, early AGs had the harness going through guides on the top of the seat that wore out the belts.

The retractor makes it difficult to raise and lower the rear seat.

• Rear seats: The committee decided they needed extra padding.  So much padding that putting the back seat down is difficult and the supports on the spar cut the leather.

• It should have been fitted with a 180 hp IO360 and constant speed prop.

Inspecting the flap mechanism under the rear seat is not any fun at all.

• Using the Vacuum Filter mounting bolt as the main ground for the electical system.  What a major DUMB idea.

• Running the oil pressure hose from the right side of the engine, behind the oil filter, to a transducer on the far left side of the engine compartment.

Now, everytime you want to change the oil filter you have to wrestle with the oil pressure hose.

• Putting the electric primer directly behind the oil filter.  As if working around the oil pressure hose isn't enough.

• Two airboxes instead of one. The original AA5B airbox is likely best engineered piece on the plane.  It's complex.  But, it's near perfect.  So, the commettee decides...

The reason for 'perceived High Cylinder Head Temps must be the carb air inlet being taken off of #3.  I mean, it just MUST be stealing air from #3.  Easiest solution, move the inlet.  No enginnering involved. Just move the inlet.  What do they do? They move the inlet to the bottom of the cowling to "a location where the air is accelerating" and, you guessed it, lowering the pressure. Not by some.  But by a minimum of 1.5 inches of manifold pressure.  What a major DUMB idea.  The location of the AA5B inlet is behind #3 cylinder where total pressure is the highest.

But, But, But, what about the high CHTs?  At 140 knots there is about 4400 cubic feet per minute of air avaiable at the cooling air inlet.  At most, an O360 will consume about 300 cubic feet per minute. Do you honestly think it's going to make a difference?  Absolutely no engineering effort was made to address cylinder head temperatures.

• 28 volts: Yes, there is some logic for 28 volts. Less current=smaller wire. But, from a practical point of view, if your fully loaded Cadillac can live with 12 volts, so can your Tiger.

• It should have been fitted with a 180 hp IO360 and constant speed prop.

AG5B:  Later AGs got a second chance to make it more user friendly.  Nope.  Missed it by 'this' much.  Must have been the same committee.

• It should have been fitted with a 180 hp IO360 and constant speed prop.  But, I repeat myself.  You had two chances to make this a more desireable plane.

• Instrument panel layout, in the age of moving map navigation, putting the avionics in front of the co-pilot instead of in the middle of the panel makes no sense.

I applied my idea of the perfect panel to N28747.  Check out Perfection-N28747 on the TeamGrumman Page.

• The engine gauges are better. But, there is a LOT of wasted real estate on the top of the panel.  Engine gauges should be horizontal in front of the pilot.

• Filling the entire side of the plane with Bondo to hide the body seams.  I can see it now (in committee, of course). Hey guys, let's kill some climb performance by adding 100 lbs

of Bondo to the side of the plane.  Hell, it's usually only the pilot that flies so he won't need the extra useful load. AND, it will look really cool with the flat sides." 

I don't know about you, but I'm damn proud of my 'glued together' airplane.  You can examine my seams any day.

AA5x:  For the most part, the '78, '79, & '77 Grummans are the cream of the crop.  Fast, great utility, easy to work on.

• Putting a cigarette lighter in a plane is stupid anyway.  Putting in one that is impossible to remove with the console side panels in place is idiodic. 

Let's see. To remove the side panels, first remove the top plastic cover. To remove the top plastic cover, first remove the cigarette lighter. To remove the cigarette lighter, first remove the side panels. Say what???????

• Putting the microphone jack (in the left console) where it can't be reached to remove, tighten, or reinstall, is dumb.  The enire console needs to be opned to get to the jack.

• Putting the flap motor and bracket in the extreme left corner so that adjusting the left flap takes 30 minutes instead of the 3 minutes it takes to adjust for the right flap. 

If they had notched the top of the bellcrank which actuates the flaps by 1/2 inch, they could have saved hours in assembly.  WHY? Because a ratchet and socket could then be used. 

Over the production life , they'd have saved thousands of dollars.

• Inspection cover in baggage compartment (Tiger):  The inspection panel in the Tiger under the carpet.  This adds a LOT of time to inspecting that area. 

On the Cheetah, the inspection cover is on the outside, making it a lot easier to inspect. 

• Plastic eyebrows:   This idea just wasn't thought out.  Using a plastic that warps in the sun.  DUMB. 
. . . . covering the underside of the eyebrow with more plastic.  Changing a light bulb is 30 minutes instead of 30 seconds.

• Metal exit ramps (78-79) for the cooling air.   Cheaper, yes.  Less efficient, yes.  BUT, it doesn't absorb vibration. Cracks on the lower right side of the cowling are inevitable. 

Only the airplane owner loses.

• Figure this one out.  On the inside of the fuselage, just above the baggage door, is an extruded piece of aluminum that is bonded and riveted into place.  What is it there for? 

If they needed strength, why not install it so it doesn't protrude into the channel where the plastic trim goes.  The plastic will never fit well in this area.

• Wheel pants with over 140 separate parts PER WHEEL PANT!

• Plastic main gear wheel pants that require a lead weight for balance. I mean, every plane needs to carry dead weight.  Right?

• Defroster vents with an oval mounting for a round hose with only a 3/8 inch lip to mount to.

• Not splitting the lower cowling vertically.  Removing and installing the lower cowling repeatedly damages the lower cowling.

This is especially true on a Cheetah because it requires the cowling to be bent out of the way of the exhaust pipe while working around the airbox hangin down.

• A nose gear boot that doesn't easily slide (out-of-the-way) down the nose gear to make removing the cowling easier.   . . (I fixed this with a fiberglass nose strut fairing)

• Under-sized outboard aileron bearings.  They should be the same as the inner bearing.

• Making the hat shelf install before the rear window mouldings. It's real easy to inspect the aft fuselage/empennage with the hat shelf out. 

Why not install the hat rack so that it comes out first instead of last? Then, during an inspection, remove the hat shelf and gain easy access. This would also eliminate the inspection hole.  This was fixed on the later AG5B Tigers.  Way to go Tiger LLC.

• AA5B Tiger:  Square openings on both ends of the carb air inlet duct. Then using a round hose to connect them.

Then routing it through the engine mount so that it has to be deformed to half it's useful area.