As the project with my MD500 continues, I am continually amazed at the complex nature of some seemingly very simple repairs and everything that has to go into the repair process for each repair.  This includes design of the repair, documentation of the repair itself and the exact procedures to be used for the repair, justification for the repair, margin of safety evaluations for the repair, references to design documents, structure catalogs and more. All of this has to be documented (in this case a full 15 pages of documentation, pictures, figures, evaluations, metal and alloy material statements) and then forwarded to the FAA DAR (Designated Airworthiness Representative) for approval BEFORE the repair can be done.

I glance at something and think to myself – that looks like a 5 minute repair job. A little bondo, a little paint and hey, we are back in business. As part of this process with my 500, the folks at PHI are teaching me a great deal about the process a repair has to go through from start to finish. I thought I would take this opportunity to share with you the process for just a single, simple repair.

Lets start with what I assumed would be a simple repair. In the MD500, there is a cooling fan and a shroud and ducting that sits behind the back passenger area. This shroud and ducting has a tendency in the 500 to rub on what is commonly referred to as the Station 124 Canted Beam. This beam is part of the main structure of the helicopter and hence is pretty important to the overall airworthiness of the aircraft.

Take a look at the pictures below. This is the “damage” caused by a little rubbing of a cooling duct over years and thousands of hours of service.

Station 124 Canted Beam Damage

Station 124 Canted Beam Damage

Station 124 Canted Beam Damage

Station 124 Canted Beam Damage

Now I don’t know about the rest of you, but a little scratch .008″ deep just does not set my alarm bells ringing…heck the neighbor’s cat did worse than that to my BWM the other day when it decided to run across its hood first thing in the morning! Thankfully, I am not the one that decides which repairs are important and which repairs can be corrected with a little 80 grit and some white rustoleum! This canted beam is integral to the structural integrity of the 500 and it required repair.

As I said earlier, PHI went to work putting together the necessary documentation showing how they intended to make the repair, proved via engineering calculations that the tensile strength of the repair would be the same or better than the total replacement of the canted beam and received FAA DAR authorization to complete the repair.

(Click on the sheet for a larger view)

Station 124 Canted Frame Illustration

Repair Report for Station 124

In the above document pages, you can see where PHI is using the MD documentation to show the exact location of the repair to be completed and just a small part of the planning information that went into the repair showing all of the documents they used for the engineering justification. Further we see an exact CAD drawing of what the repair will look like when it has been completed.

Figure 4 Showing Repair

As you can see from just a few pages of the 15 page repair report, there is a lot of information and engineering that has to go into a repair like this. In the end, failure to get it right can cause serious consequences for the crew and passengers aboard the 500 should the repair fail in flight.

Below are the pictures of the repair as it progressed from one stage to the other. I hope anyone reading this can appreciate the nature of the repair along with my fascination at the high quality workmanship that went into this repair. This is indicative of all the work that has gone into my 500 to date!

Station 124 Canted Beam before repair work starts

Station 124 Canted Beam before repair work starts

This is the canted beam before they started any repair work on it. You can see both wear marks noted by blue tape here to identify the exact area of damage.


Station 124 Canted Beam after prepping for repair

Station 124 Canted Beam after prepping for repair

This is the canted beam after it had been prepped for its repair. It had to be cleaned, cured and then epoxy primer and adhesive was applied prior to installation of the repair pieces.

Doublers in Place

Doublers in Place

Here you can see that the doublers and shims needed for the repair have been put into place and they have started to install the rivets and Hi-Lok pins that will hold the entire repair in place.

View of work from other side

View of work from other side

Here is a view of the repair work from the other side of the picture above. You can see the bottom row of rivets/Hi-Lok pins are already in place and the epoxy adhesive is also visible.

And now you can see the extent of the completed repair:

Completed Repair

Completed Repair

Completed Repair

Completed Repair

Completed Repair

Completed Repair

Completed Repair

Completed Repair

Now I don’t know about the rest of you, but I feel much better with this style of repair over my “80 grit and some white rustoleum” repair. And if you happen to see a grey BWM with a white streak across the hood driving around Mesa one day, you will know that’s me!

Richard J. Sears

Hi – I am the author – Richard Sears. I have been a pilot and flight instructor for over 20 years!

If you live in the San Diego area and would like to arrange a free airplane or helicopter flight for your child (age 8 to 18) through the EAA Young Eagles program please email me at richard@sears.net

If you are a Scout Master, I can work with your troop on the Aviation Merit Badge and provide all ground training and flights necessary to meet the latest requirements of the Aviation Merit Badge. I am a registered Merit Badge Counselor with the BSA San Diego – Imperial Council.

All my flight time is donated, there is no cost to the parents or the troop.

Parents are always welcome to ride along and get hooked!