Why are TPMS not allowed on certified aircraft

[Dream to fly]

I was repairing a trike for a buddy of mine after having a rear wheel go flat and damage the rim and suspension.  He was hell bent on not letting that happen again and installed a 3 sensor TPMS system that screws on to the valve stems and transmits to a display on the handle bars.  I thought it was a great idea especially for a low wing and looked up systems for aircraft.  As expected it is not allowed on certified aircraft.  WHY?  

[jlunseth]

Would you like to have your GPS receive its position from your tires? Or your radio squeal at you? The reason is interference. I am sure if someone were to devise a system that generates no interference and is willing to go through the STC process to prove it up, that you could do it.

[toto]

What's the operational scenario?

You're flying along and your TPMS shows that one tire is getting low. Do you land immediately? Or divert to the nearest airport with light mx available?

In a car, you pull over to a place with an air pump and top it off. Then drive a bit more and see if it's holding air. I'm not sure what I would do in an aircraft in the same situation, other than perhaps try to land as gingerly as possible to avoid the tire coming apart or doing damage to the wheel. 

I guess it would be nice to avoid the flat-tire surprise on landing, but I hope it's a very rare case that a tire was perfect on preflight and then developed a major leak enroute. 

(Not trying to be a wet blanket here, just thinking out loud... )

 

 

[N201MKTurbo]

1 hour ago, Dream to fly said:

I was repairing a trike for a buddy of mine after having a rear wheel go flat and damage the rim and suspension.  He was hell bent on not letting that happen again and installed a 3 sensor TPMS system that screws on to the valve stems and transmits to a display on the handle bars.  I thought it was a great idea especially for a low wing and looked up systems for aircraft.  As expected it is not allowed on certified aircraft.  WHY?  

Who says or isn’t allowed on aircraft? People put all kinds of stuff that isn’t certified in their aircraft.

[N201MKTurbo]

Get these guys to put your Mooney on their STC.

https://www.meggitt.com/technology/wtps/

 

[Tim Jodice]

58 minutes ago, toto said:

I guess it would be nice to avoid the flat-tire surprise on landing, but I hope it's a very rare case that a tire was perfect on preflight and then developed a major leak enroute. 

 

 

It is rare but it does happen. Had I known it was coming I would have landed a little different mainly in keeping that wheel off until it was going as slow as possible. Likely would have avoided lower gear door damage.

[Shadrach]

https://www.craneae.com/tire-pressure-and-brake-temperature-systems
 

Perhaps you might persuade the local FSDO to grant field approval.

[Vance Harral]

1 hour ago, toto said:

I guess it would be nice to avoid the flat-tire surprise on landing, but I hope it's a very rare case that a tire was perfect on preflight and then developed a major leak enroute.

One cause of this is finding a tire a little low on preflight, adding some air, and having the Schrader valve not quite close on removing the chuck.  An hour or more later, you land on an unexpectedly flat tire.  Ask me how I know.

I no longer air up tires immediately before a flight.  If a tire is slightly low, I fly as-is, and air it up at the end of the flight.

[aviatoreb]

I had a blowout flat at Portland Me about 3 years ago on rollout.  It was a fight to keep it on the runway as it was pulling very hard to the left. No damage other than minor gear door scratched and a horrifically expensive tire change and emergency tow service on a Sunday.

Closed the runway and tower sent the commercial flights on go around. I am sure they spent more extra for fuel than I spent on tires.

plus I was checking in to homeland border patrol do we dutifully waited at the airplane until border patrol figured out what to do with us.

E

[Raymond J1]

8 hours ago, Dream to fly said:

Je réparais un tricycle pour un de mes copains après avoir fait tomber une roue arrière à plat et endommager la jante et la suspension. Il était déterminé à ne pas laisser cela se reproduire et a installé un système TPMS à 3 capteurs qui se visse sur les tiges de valve et se transmet à un écran sur le guidon. J'ai pensé que c'était une excellente idée en particulier pour une aile basse et j'ai recherché des systèmes pour avions. Comme prévu, il n'est pas autorisé sur les avions certifiés. POURQUOI?  

This system adds an extension to the valve and a bit of mass too. So there is a question of swinging and then holding the valve in the first moments of the touchdown and also during takeoff. And you know that our rims do not have too much inner diameter to accommodate a lot of things.

[Dream to fly]

Who says or isn’t allowed on aircraft? People put all kinds of stuff that isn’t certified in their aircraft.

The few systems I could find for aircraft specifically say for experimental planes only. I would think having a system that has been well tested on vehicles of all shapes and sizes for all sorts of duties I would think it would be a no brainier. As for people putting things in or on their airplane that can't happen. It's illegal and the book written by the gods says so.

Sent from my E6910 using Tapatalk

[Dream to fly]

What's the operational scenario?
You're flying along and your TPMS shows that one tire is getting low. Do you land immediately? Or divert to the nearest airport with light mx available?
In a car, you pull over to a place with an air pump and top it off. Then drive a bit more and see if it's holding air. I'm not sure what I would do in an aircraft in the same situation, other than perhaps try to land as gingerly as possible to avoid the tire coming apart or doing damage to the wheel. 
I guess it would be nice to avoid the flat-tire surprise on landing, but I hope it's a very rare case that a tire was perfect on preflight and then developed a major leak enroute. 
(Not trying to be a wet blanket here, just thinking out loud... )
 
 

It should be a rare case but I have towed two aircraft off the runway here in ND where the tire lost all the air after takeoff and the pilot didn't know about it till he landed and had a handful of airplane to deal with. A simple $240 system that adds little to nothing for weight seems like cheap insurance. I was just wondering why it would be an issue.

Sent from my E6910 using Tapatalk

[ArtVandelay]

I thought anything not permanently attached to the airplane is okay (cameras, etc)? So a screw on device to monitor air pressure seems to fall into that category. Obviously you need to experiment to insure it doesn’t affect com or nav frequencies.

[carusoam]

Beringer brakes

A company that makes brake systems for experimental aircraft...

has announced a new product to measure air pressure remotely from inside their wheels and tires....

 

Of course the product is so new... their website has nothing about it...

First step in the certified world...

Expect SR22 for some reason...

 

Apparently, this product is good for the wheel pant guys....  who never check their air pressure...   

Best regards,

-a-

@Dream to fly Joe, you have a great idea here...

[GeeBee]

The problem I see with the screw on types is you have replaced the Schrader valve, which is self closing, backed up with a sealing cap, with a cap which can leak and is the sole source against leakage. I see more risk  with the system than without it.

We had tire pressure monitors on the A330. The company removed them claiming they were "too maintenance intensive". Now that may sound like the system required a lot of care, but what they meant was too many pilots calling maintenance for a pressure check, especially on hot tires. Try as they may to say the pressure values were valid only on a cold tire, you can't really know if the airplane landed 6 hours ago how much residual heat was in the tire. They also had little gauges on the 737NG tires, and they turned out to be a bust, because they failed too often.

[JimB]

6 hours ago, carusoam said:

Beringer brakes

A company that makes brake systems for experimental aircraft...

has announced a new product to measure air pressure remotely from inside their wheels and tires....

 

Of course the product is so new... their website has nothing about it...

First step in the certified world...

Expect SR22 for some reason...

 

Apparently, this product is good for the wheel pant guys....  who never check their air pressure...   

Best regards,

-a-

@Dream to fly Joe, you have a great idea here...

There is a brief overview on there. https://www.beringer-aero.com/en/sensair 

[A64Pilot]

On 12/27/2020 at 1:47 PM, Vance Harral said:

One cause of this is finding a tire a little low on preflight, adding some air, and having the Schrader valve not quite close on removing the chuck.  An hour or more later, you land on an unexpectedly flat tire.  Ask me how I know.

I no longer air up tires immediately before a flight.  If a tire is slightly low, I fly as-is, and air it up at the end of the flight.

I had that exact scenario on the C-210, the nose wheel. it was completely flat but luckily did no damage.

‘The rest of the story is that if I had a metal valve cap installed, you know the kind that’s painted yellow and has an O-ring in the cap, then my leak would have been very slow and been detectable.

[MooneyMitch]

Didn’t our Space Shuttle have some form of tire pressure monitor? 
 

Not they the crew could pull over and call AAA! 

[A64Pilot]

Everything is an issue with the FAA, until or unless through the STC process it’s been shown to cause no harm.

‘I’ve done many EMI/EMC test flights, it’s time consuming but not all that difficult, that and am electrical DER and some paperwork and time and it’s likely you will get your STC.

‘There is something called unintended consequences that the FAA is trying to guard against.

‘Many people think that say an oil additive for example being FAA approved is some kind of acknowledgement that it works or is good etc. and it’s not. All that has been done is to prove that it causes no harm

[A64Pilot]

On 12/28/2020 at 3:22 AM, ArtVandelay said:

I thought anything not permanently attached to the airplane is okay (cameras, etc)? So a screw on device to monitor air pressure seems to fall into that category. Obviously you need to experiment to insure it doesn’t affect com or nav frequencies.

That’s not true, in fact a camera on the outside of the aircraft is very much not legal, it’s an external load and that has its own special criteria. Now before someone gets upset about how an a little Gopro be an external load,I can tell you that a game tracking antenna mounted on the struts of a SuoerCub has been forever, an external load 

‘The FAA has a name for what your saying it basically says anything attached by simple means although that’s not the word, and I seriously doubt that it’s in a FAR, maybe an AC. An AC is not regulatory although they treat them as such, but as they are Advisory only, the FAA believes it absolves them of responsibility, and as it’s not Law an AC is a whole lot easier to get published.

‘For some reason a little more than a decade ago FAA inspectors became very concerned about liability, they believe they can be held personally liable for their work, and since then it’s gotten a lot harder to get anything from them. I’m sure they can, but it would be real tough I think to make it stick, and not to be ugly but its also unlikely they would have the assets to make it worth a Lawyers time.

‘So far as I know of the FAA has ignored it, but no one has been hit in the head from a camera falling off of a airplane yet, but when they do expect some kind of response

[Yetti]

On 12/27/2020 at 12:47 PM, Vance Harral said:

One cause of this is finding a tire a little low on preflight, adding some air, and having the Schrader valve not quite close on removing the chuck.  An hour or more later, you land on an unexpectedly flat tire.  Ask me how I know.

I no longer air up tires immediately before a flight.  If a tire is slightly low, I fly as-is, and air it up at the end of the flight.

Schrader valves are not designed to keep air pressure in, that is what the caps are for.

[StevenL757]

If you really want to do it right?  Try Crane Aerospace & Electronics' product...currently used on the 737MAX, 777, and 787.  :-)

[A64Pilot]

How about central tire inflation systems? The new generation of Army trucks both monitor and can adjust tire pressure on the fly, flip a switch for off road, flip it back for highway.

‘I’ve seen several big rigs that appear to have the same systems, look for hoses connected to the scraper valves on the big trucks, I assume that’s a central inflation system

[GeeBee]

There goes all the useful load.

 

[JimB]

22 hours ago, A64Pilot said:

That’s not true, in fact a camera on the outside of the aircraft is very much not legal, it’s an external load and that has its own special criteria. Now before someone gets upset about how an a little Gopro be an external load,I can tell you that a game tracking antenna mounted on the struts of a SuoerCub has been forever, an external load 

‘The FAA has a name for what your saying it basically says anything attached by simple means although that’s not the word, and I seriously doubt that it’s in a FAR, maybe an AC. An AC is not regulatory although they treat them as such, but as they are Advisory only, the FAA believes it absolves them of responsibility, and as it’s not Law an AC is a whole lot easier to get published.

‘For some reason a little more than a decade ago FAA inspectors became very concerned about liability, they believe they can be held personally liable for their work, and since then it’s gotten a lot harder to get anything from them. I’m sure they can, but it would be real tough I think to make it stick, and not to be ugly but its also unlikely they would have the assets to make it worth a Lawyers time.

‘So far as I know of the FAA has ignored it, but no one has been hit in the head from a camera falling off of a airplane yet, but when they do expect some kind of response

You are 100% right on all of that concerning the FAA. It does seem they are trying to loosen up a bit with their Non Required Safety Enhancing Equipment (NORSEE) policies but a lot of inspectors do feel they may be held personally responsible so they have zero interest in sticking their necks out. 

I do wonder if there have been any studies on experimental aircraft to determine how many accidents are caused by parts or products used that aren't FAA approved/accepted/authorized/certified. I am going to guess that if there is some data on that it would show that there is virtually no difference in the failure rate of FAA approved vs not approved parts.