redcatcher27 Posted June 11, 2020 Report Share Posted June 11, 2020 Welp. I guess you learn something new every day. I took my 1968 M20F in for an oil change, installation of a new (to me) vacuum step actuator, and 24 month IFR certification of the static, transponder, altimeter. Mind you, I had been flying for almost three years of ownership with the old altimeter... Aircraft logs showed that it had been IFR certified roughly every 2 years since it was installed in 2004. Came home with a new altimeter, after I was told my old one wasn't certified for IFR flight. They told me why they thought it wasn't, but do you know or can you guess? BTW, the old altimeter was p/n 5934P-A56 and the new one is p/n 5934A-1. Or maybe I just got bamboozled? Anyway, the cert along with the new altimeter cost me less than .5 AMU, so I suppose I am happy. Quote Link to comment Share on other sites More sharing options...
Hank Posted June 11, 2020 Report Share Posted June 11, 2020 No clue on the certification, but mine looks like the bottom one. Don't think I've seen one with tick marks every 50 feet, only recall seeing the 20-foot tickmarks. 2 Quote Link to comment Share on other sites More sharing options...
redcatcher27 Posted June 11, 2020 Author Report Share Posted June 11, 2020 1 minute ago, Hank said: No clue on the certification, but mine looks like the bottom one. Don't think I've seen one with tick marks every 50 feet, only recall seeing the 20-foot tickmarks. So, for clarity, the top one was the OLD one. T he bottom one, with the 20' tick marks is my NEW one. Quote Link to comment Share on other sites More sharing options...
Hank Posted June 11, 2020 Report Share Posted June 11, 2020 Just now, redcatcher27 said: So, for clarity, the top one was the OLD one, the bottom one, with the 20' tick marks is my NEW one. Yes, I understood that. Never seen one with 50' tickmarks. Surely that's not what they didn't like? I would suspect something internal to the unit that's not visible from the left seat. Quote Link to comment Share on other sites More sharing options...
redcatcher27 Posted June 11, 2020 Author Report Share Posted June 11, 2020 No, that's it! That's what they indicated to me - that I needed one with 20 foot tick marks! But perhaps there's an internal issue too? I don't know. Quote Link to comment Share on other sites More sharing options...
hammdo Posted June 11, 2020 Report Share Posted June 11, 2020 I think part of the issue has to do with the 75' requirement for altimeter accuracy in IFR use. 20' increments make it easier to comply with the rules vs 50'. That is probably why... -Don 2 Quote Link to comment Share on other sites More sharing options...
Floyd Posted June 11, 2020 Report Share Posted June 11, 2020 The Air Force E3 aircraft I used to fly had 50 ft marks. Flew alot of IFR. 1 Quote Link to comment Share on other sites More sharing options...
Hank Posted June 11, 2020 Report Share Posted June 11, 2020 5 hours ago, Floyd said: The Air Force E3 aircraft I used to fly had 50 ft marks. Flew alot of IFR. U.S. military aircraft are not certified by the FAA, and pilots have the option of obtaining FAA pilot certificates. 1 Quote Link to comment Share on other sites More sharing options...
jamesm Posted June 12, 2020 Report Share Posted June 12, 2020 yeah you certainly don't want to get the line for the vacuum step confused with static line on the airspeed indicator... oops .... I know a guy who did that .... I had never seen the air speed wind up that fast :-O .... I knew immediately what happen the poor air speed indicator it wound up so quickly. I can tell you that after that experience, I can tell you that l paid closer attention on the detail to my labeling techniques and vacuum line to step had label after that.. 1 Quote Link to comment Share on other sites More sharing options...
drapo Posted June 12, 2020 Report Share Posted June 12, 2020 From what I understand, you need a «sensitive altimeter» and that is the definition: Sensitive altimeters have a 100-foot scale (20-foot tick marks) as their most precise display. In Canada, there was a study done and they issued the following rule, but I'm not sure if it is interpreted the same way in the US, but usually, there are not such dramatic differences between our regulations: The intent of the Transport Canada Aviation (TCA) policy promulgated in the November 24, 1981 memo from Headquarters to the Regions on aircraft altimeter markings and in APL No. 2 is still valid and is specified below. The following criteria defines Transport Canada requirements for altitude increment markings for sensitive altimeters: For all operations to Category II limits or lower, altimeters shall be marked in altitude increments not to exceed 20-feet; and For all VFR operations, which require a sensitive altimeter and all IFR operations to Category I limits, altimeters shall be marked in altitude increments not exceeding 50-feet. 1 1 Quote Link to comment Share on other sites More sharing options...
redcatcher27 Posted June 12, 2020 Author Report Share Posted June 12, 2020 Great explaination! Thanks so much. Quote Link to comment Share on other sites More sharing options...
carusoam Posted June 12, 2020 Report Share Posted June 12, 2020 Funny thing is... I was familiar with the rules... displaying 20’ accuracy... for use in IFR... I Know my O complies with that rule as well.... But, the 50’ altimeter markings sure look familiar... probably what my 65 M20C had... What is the purpose of the hashed lines opposite of the 10k’ pointer? (Just to show where the pointer is in the case it gets hidden?) Why is one wider than the other? Best regards, -a- Quote Link to comment Share on other sites More sharing options...
redcatcher27 Posted June 12, 2020 Author Report Share Posted June 12, 2020 I think that manufacturers added the hashed lines to highlight that the aircraft is at a low altitude, in a way that's much easier and quicker for the pilot than 'parsing' multiple hands on the altimeter face. Different widths - the hashed area gets bigger as you get lower. Quote Link to comment Share on other sites More sharing options...
HRM Posted June 12, 2020 Report Share Posted June 12, 2020 This one has been thru many an IFR cert...what was that shops name? Don't want to go there. 1 Quote Link to comment Share on other sites More sharing options...
redcatcher27 Posted June 12, 2020 Author Report Share Posted June 12, 2020 53 minutes ago, HRM said: This one has been thru many an IFR cert...what was that shops name? Don't want to go there. I'd rather not say here, but if you pm me, I'll be glad to tell you. 1 Quote Link to comment Share on other sites More sharing options...
PT20J Posted June 12, 2020 Report Share Posted June 12, 2020 From the Instrument Flying Handbook glossary: Sensitive altimeter. A form of multipointer pneumatic altimeter with an adjustable barometric scale that allows the reference pressure to be set to any desired level. Cessna used to use sensitive altimeters with 50’ markings. They were certified IFR. When a shop tells you that you have to change a part because it’s not legal, it’s always a good idea to ask them to show you the reg. Sometimes mechanics are wrong. Sometimes pilots are unaware of a rule change. Either way, everyone learns something. Skip 5 1 Quote Link to comment Share on other sites More sharing options...
EricJ Posted June 12, 2020 Report Share Posted June 12, 2020 A DPE I've known most of my life has a 1960 C210A that she has owned for more than fifty years. Her husband was a PanAm 747 captain and had been an F-104 pilot in the Air Force. Somewhere along the way he snagged an airspeed indicator from an F-104 and they put it in the 210. It was in there since I first saw it in the mid-1970s and I always thought it was pretty cool. They had the red line (Vne) tape on the glass as required. I talked to her for the first time in a while a year or so ago and she was fuming mad because an IA made her take that airspeed indicator out and put one in that had all of the proper arcs marked. So, yeah, there can be differences in opinions. I think the red line was all that was required, but I haven't looked it up. 1 Quote Link to comment Share on other sites More sharing options...
N201MKTurbo Posted June 12, 2020 Report Share Posted June 12, 2020 3 hours ago, EricJ said: A DPE I've known most of my life has a 1960 C210A that she has owned for more than fifty years. Her husband was a PanAm 747 captain and had been an F-104 pilot in the Air Force. Somewhere along the way he snagged an airspeed indicator from an F-104 and they put it in the 210. It was in there since I first saw it in the mid-1970s and I always thought it was pretty cool. They had the red line (Vne) tape on the glass as required. I talked to her for the first time in a while a year or so ago and she was fuming mad because an IA made her take that airspeed indicator out and put one in that had all of the proper arcs marked. So, yeah, there can be differences in opinions. I think the red line was all that was required, but I haven't looked it up. The TCDS probably mandates all the arcs. 1 Quote Link to comment Share on other sites More sharing options...
N201MKTurbo Posted June 12, 2020 Report Share Posted June 12, 2020 The TCSD specifies the airspeed indicator must be marked according to CAR 3-756. As you can see, marking the glass is allowed. § 3.756 Instrument markings. The instruments listed in §§ 3.757-3.761 shall have the following limitations marked thereon. When these markings are placed on the cover glass of the instrument, adequate provision shall be made to maintain the correct alignment of the glass cover with the face of the dial. All arcs and lines shall be of sufficient width and so located as to be clearly and easily visible to the pilot. § 3.757 Air-speed indicator. (a) True indicated air speed shall be used: (1) The never-exceed speed, Vne—a radial red line (see § 3.739). (2) The caution range—a yellow arc extending from the red line in (1) above to the upper limit of the green arc specified in (3) below. (3) The normal operating range—a green arc with the lower limit at Vs1, as determined in § 3.82 with maximum weight, landing gear and wing flaps retracted, and the upper limit at the maximum structural cruising speed established in § 3.740. (4) The flap operating range—a white arc with the lower limit at Vso as determined in § 3.82 at the maximum weight, and the upper limit at the flaps-extended speed in § 3.742. 1 Quote Link to comment Share on other sites More sharing options...
EricJ Posted June 12, 2020 Report Share Posted June 12, 2020 Just now, N201MKTurbo said: The TCSD specifies the airspeed indicator must be marked according to CAR 3-756. As you can see, marking the glass is allowed. § 3.756 Instrument markings. The instruments listed in §§ 3.757-3.761 shall have the following limitations marked thereon. When these markings are placed on the cover glass of the instrument, adequate provision shall be made to maintain the correct alignment of the glass cover with the face of the dial. All arcs and lines shall be of sufficient width and so located as to be clearly and easily visible to the pilot. § 3.757 Air-speed indicator. (a) True indicated air speed shall be used: (1) The never-exceed speed, Vne—a radial red line (see § 3.739). (2) The caution range—a yellow arc extending from the red line in (1) above to the upper limit of the green arc specified in (3) below. (3) The normal operating range—a green arc with the lower limit at Vs1, as determined in § 3.82 with maximum weight, landing gear and wing flaps retracted, and the upper limit at the maximum structural cruising speed established in § 3.740. (4) The flap operating range—a white arc with the lower limit at Vso as determined in § 3.82 at the maximum weight, and the upper limit at the flaps-extended speed in § 3.742. So now I especially like that she got to use the other one for fifty years. I knew it had to have Vne marked which could be done on the glass, as long as there's an alignment mark on the glass and bezel. The rest is probably dependent on the certification details for each aircraft. That's all magic IA stuff, right? 1 Quote Link to comment Share on other sites More sharing options...
N201MKTurbo Posted June 12, 2020 Report Share Posted June 12, 2020 4 minutes ago, EricJ said: So now I especially like that she got to use the other one for fifty years. I knew it had to have Vne marked which could be done on the glass, as long as there's an alignment mark on the glass and bezel. The rest is probably dependent on the certification details for each aircraft. That's all magic IA stuff, right? Yes, The IA test is all about looking up this stuff. There is practically nothing about fixing airplanes! 1 Quote Link to comment Share on other sites More sharing options...
tmo Posted June 22, 2020 Report Share Posted June 22, 2020 On 6/12/2020 at 8:47 PM, N201MKTurbo said: There is practically nothing about fixing airplanes! That was done during A&P, right? Just so I don't get confused on the distinctions... Quote Link to comment Share on other sites More sharing options...
N201MKTurbo Posted June 22, 2020 Report Share Posted June 22, 2020 3 hours ago, tmo said: That was done during A&P, right? Just so I don't get confused on the distinctions... I was talking about the test for the Inspection Authorization. 1 Quote Link to comment Share on other sites More sharing options...
1964-M20E Posted June 25, 2020 Report Share Posted June 25, 2020 Well my 64E had the 50' markings and was certified IFR, my 67F has the 20' markings IFR cert tomorrow if weather cooperates. No wonder I find it harder to tell what altitude I'm at with my 67F. 1 Quote Link to comment Share on other sites More sharing options...
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